2020-10-29T05:16:37Zhttp://edoc.mpg.de/ac_p_oai.ploai:edoc.mpg.de:2048802005-07-0837:954
Two-Loop Bethe logarithms for higher excited S levels
Jentschura, Ulrich David
expertsonly
Processes mediated by two virtual low-energy photons contribute quite significantly to the energy of hydrogenic S states. The corresponding level shift is of the order of (alpha/pi)2 (Zalpha)6 mec2 and may be ascribed to a two-loop generalization of the Bethe logarithm. For 1S and 2S states, the correction has recently been evaluated by Pachucki and Jentschura [Phys. Rev. Lett. 91, 113005 (2003)]. Here, we generalize the approach to higher excited S states, which in contrast to the 1S and 2S states can decay to P states via the electric-dipole (E1) channel. The more complex structure of the excited-state wave functions and the necessity to subtract P-state poles lead to additional calculational problems. In addition to the calculation of the excited-state two-loop energy shift, we investigate the ambiguity in the energy level definition due to squared decay rates.
©2004 The American Physical Society
2004
Article
http://edoc.mpg.de/204880
Physical Review A, v.70 (2004)
oai:edoc.mpg.de:2048812005-07-0837:954
Nonrelativistic QED Approach to the Bound-Electron g Factor
Pachucki, Krzysztof
Jentschura, Ulrich David
Yerokhin, Vladimir A.
expertsonly
Within a systematic approach based on nonrelativistic quantum electrodynamics, we derive the one-loop self-energy correction of order alpha(Zalpha)4 to the bound-electron g factor. In combination with numerical data, this analytic result improves theoretical predictions for the self-energy correction for carbon and oxygen by an order of magnitude. Basing on one-loop calculations, we obtain the logarithmic two-loop contribution of order alpha2(Zalpha)4ln[(Zalpha)–2] and the dominant part of the corresponding constant term. The results obtained improve the accuracy of the theoretical predictions for the 1S bound-electron g factor and influence the value of the electron mass determined from g-factor measurements.
©2004 The American Physical Society
2004
Article
http://edoc.mpg.de/204881
Physical Review Letters, v.93 (2004)
oai:edoc.mpg.de:2048822006-08-2137:954
Magnetic and thermal influences on collective resonance fluorescence
Macovei, Mihai
Evers, Jörg
Keitel, Christoph Helmut
expertsonly
The quantum properties of a collection of dipole-interacting three-level V- and $\Lambda$-type atoms are investigated in the presence of external coherent sources and a thermal bath. It is demonstrated that both the steady-state collective populations and the spectral features of these samples can be manipulated by varying the temperature or especially the atomic-level spacings by, e.g., static magnetic fields.
© EDP Sciences 2004
2004
Article
http://edoc.mpg.de/204882
Europhysics Letters, v.68, 391-397 (2004)
oai:edoc.mpg.de:2048832005-07-0837:954
Double-EIT ground-state laser cooling without blue-sideband heating
Evers, Jörg
Keitel, Christoph Helmut
expertsonly
We discuss a laser cooling scheme for trapped atoms or ions which is based on double electromagnetically induced transparency (EIT) and makes use of a four-level atom in tripod configuration. The additional fourth atomic state is coupled by a strong-coupling laser field to the upper state of the usual three-level setup of single-EIT cooling. This effectively allows to create two EIT structures in the absorption spectrum of the system to be cooled, which may be controlled by the coupling laser field parameters to cancel both the carrier- and the blue-sideband excitations. In leading order of the Lamb-Dicke expansion, this suppresses all heating processes. As a consequence, the double-EIT scheme can be used to lower the cooling limit by a factor of order of the Lamb-Dicke parameter squared as compared to single-EIT cooling.
© EDP Sciences 2004
2004
Article
http://edoc.mpg.de/204883
Europhysics Letters, v.68, 370-376 (2004)
oai:edoc.mpg.de:2048842005-07-0837:954
Positronium in Intense Laser Fields
Henrich, Björn
Hatsagortsyan, Karen Zaven
Keitel, Christoph Helmut
expertsonly
The dynamics and radiation of positronium are investigated in intense laser fields. Our two-body quantum mechanical treatment displays the tunneling, free-evolution, and recollision dynamics of electron and positron in both the oscillating laser electric and laser magnetic field components. In spite of significant momentum transfer of the numerous incoming laser photons, recollisions of both particles are shown to occur automatically after tunneling ionization, along with substantial x-ray and gamma-ray emission during recombination and annihilation processes.
©2004 The American Physical Society
2004
Article
http://edoc.mpg.de/204884
Physical Review Letters, v.93 (2004)
oai:edoc.mpg.de:2048852005-07-0837:954
Spontaneous-emission suppression via multiphoton quantum interference
Evers, Jörg
Keitel, Christoph Helmut
expertsonly
The spontaneous emission is investigated for an effective atomic two-level system in an intense coherent field with frequency lower than the vacuum-induced decay width. As this additional low-frequency field is assumed to be intense, multiphoton processes may be induced, which can be seen as alternative transition pathways in addition to the simple spontaneous decay. The interplay of the various interfering transition pathways influences the decay dynamics of the two-level system and may be used to slow down the spontaneous decay considerably. We derive from first principles an expression for the Hamiltonian including up to three-photon processes. This Hamiltonian is then applied to a quantum mechanical simulation of the decay dynamics of the two-level system. Finally, we discuss numerical results of this simulation based on a rubidium atom and show that the spontaneous emission in this system may be suppressed substantially.
2004
Article
http://edoc.mpg.de/204885
Journal of Physics B-Atomic Molecular and Optical Physics, v.37, 2771-2796 (2004)
oai:edoc.mpg.de:2048862006-08-2137:954
Bound atomic dynamics in the MeV regime
Mocken, Guido Rudolf
Keitel, Christoph Helmut
expertsonly
The relativistic quantum dynamics of highly accelerated hydrogenic ions is investigated in the presence of a super intense counter-propagating laser pulse. Due to the large Doppler blue shift, collisions between electron and ionic core are shown to be possible in the MeV regime. This renders nuclear reactions feasible in the near future with single laser-driven ions.
2004
Article
http://edoc.mpg.de/204886
Journal of Physics B-Atomic Molecular and Optical Physics, v.37, L275-L283 (2004)
oai:edoc.mpg.de:2049252006-08-2137:954
New Limits on the Drift of Fundamental Constants from Laboratory Measurements
Fischer, M.
Kolachevsky, Nikolai
Zimmermann, Marcus
Holzwarth, Ronald
Udem, Thomas
Hänsch, Theodor W.
Abgrall, M.
Grünert, J.
Maksimovic, I.
Bize, S.
Marion, H.
Pereira Dos Santos, F.
Lemonde, P.
Santarelli, G.
Laurent, P.
Clairon, A.
Salomon, C.
Haas, Martin
Jentschura, Ulrich David
Keitel, Christoph Helmut
expertsonly
We have remeasured the absolute 1S-2S transition frequency H in atomic hydrogen. A comparison with the result of the previous measurement performed in 1999 sets a limit of (–29±57) Hz for the drift of H with respect to the ground state hyperfine splitting Cs in 133Cs. Combining this result with the recently published optical transition frequency in 199Hg+ against Cs and a microwave 87Rb and 133Cs clock comparison, we deduce separate limits on /= (–0.9±2.9)×10–15 yr–1 and the fractional time variation of the ratio of Rb and Cs nuclear magnetic moments µRb/µCs equal to (–0.5±1.7)×10–15 yr–1. The latter provides information on the temporal behavior of the constant of strong interaction.
©2004 The American Physical Society
2004
Article
http://edoc.mpg.de/204925
Physical Review Letters, v.92 (2004)
oai:edoc.mpg.de:2070852006-08-1837:954
Relativistic and radiative corrections to the Mollow spectrum
Evers, Jörg
Jentschura, Ulrich David
Keitel, Christoph Helmut
expertsonly
The incoherent inelastic part of the resonance fluorescence spectrum of a laser-driven atom is known as the Mollow spectrum [B. R. Mollow, Phys. Rev. 188, 1969 (1969)]. Starting from this level of description, we discuss theoretical foundations of high-precision spectroscopy using the resonance fluorescence light of strongly laser-driven atoms. Specifically, we evaluate the leading relativistic and radiative corrections to the Mollow spectrum, up to the relative orders of (Z)2 and (Z)2, respectively, and Bloch-Siegert shifts as well as stimulated radiative corrections involving off-resonant virtual states. Complete results are provided for the hydrogen 1S-2P1/2 and 1S-2P3/2 transitions; these include all relevant correction terms up to the specified order of approximation and could directly be compared to experimental data. As an application, the outcome of such experiments would allow for a sensitive test of the validity of the dressed-state basis as the natural description of the combined atom-laser system.
©2004 The American Physical Society
2004
Article
http://edoc.mpg.de/207085
Physical Review A, v.70, 1-20 (2004)
en
oai:edoc.mpg.de:2077022005-07-0837:954
Time Reversal and Exceptional Points
Harney, H. L.
Heiss, W. D.
expertsonly
Eigenvectors of decaying quantum systems are studied at exceptional points of the Hamiltonian. Special attention is paid to the properties of the system under time reversal symmetry breaking. At the exceptional point the chiral character of the system - found for time reversal symmetry - generically persists. It is, however, no longer circular but rather elliptic.
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2004
2004
Article
http://edoc.mpg.de/207702
info:doi/10.1140/epjd/e2004-00049-7
The European Physical Journal D, v.29, 429-432 (2004)
en
oai:edoc.mpg.de:2495302006-08-2137:954
Relativistic and radiative energy shifts for Rydberg states
Jentschura, Ulrich David
Le Bigot, Eric-Olivier
Evers, Jörg
Mohr, Peter J.
Keitel, Christoph Helmut
expertsonly
We investigate relativistic and quantum electrodynamic effects for highlyexcited bound states in hydrogen-like systems (Rydberg states). In particular, hydrogenic one-loop Bethe logarithms are calculated for all circular states
(l = n − 1) in the range 20 ≤ n ≤ 60 and successfully compared to an existing asymptotic expansion for large principal quantum number n. We provide accurate expansions of the Bethe logarithm for large values of n, for S, P and circular Rydberg states. These three expansions are expected to give any Bethe logarithm for principal quantum number n > 20 to an accuracy of five to seven decimal digits, within the specified manifolds of atomic states. Within the numerical accuracy, the results constitute unified, general formulae for quantum electrodynamic corrections whose validity is not restricted to a single atomic state. The results are relevant for accurate predictions of radiative shifts of Rydberg states and for the description of the recently investigatedlaser-dressed Lamb shift, which is observable in a strong coherent-wave light field
IOP Publishing Ltd.
2005
Article
http://edoc.mpg.de/249530
info:doi/10.1088/0953-4075/38/2/008
Journal of Physics B, v.38, S97-S105 (2005)
en
oai:edoc.mpg.de:2495332006-08-2137:954
Coherent manipulation of collective three-level systems
Macovei, Mihai
Evers, Jörg
Keitel, Christoph Helmut
expertsonly
We investigate control schemes for the dynamics of a collection of dipole-interacting three-level atoms in V- or Λ- configuration. For this, we discuss the strong-field steady-state behavior of these systems under the influence of external parameters such as the relative phase between the two applied strong driving laser fields, the ratio of spontaneous decay and incoherent pumping rates, the splitting frequency between closely spaced atomic states, or a surrounding thermal bath. We show that these may act as convenient tools to sensitively control the collective dynamics of the atoms. As applications, we analyze the fluorescence and absorption properties of the atomic samples. Finally, we discuss the transient behavior to show that the presented schemes feature a rapid system evolution as required for many applications.
The American Physical Society
2005
Article
http://edoc.mpg.de/249533
info:doi/10.1103/PhysRevA.71.033802
Physical Review A, v.71, 1-16 (2005)
en
oai:edoc.mpg.de:2495642006-01-3137:954
Emergence of Classical Orbits in Few-Cycle Above-Threshold Ionization of Atomic Hydrogen
Bauer, Dieter
expertsonly
The time-dependent Schrödinger equation for atomic hydrogen in few-cycle laser pulses is solved numerically. Introducing a positive definite quantum distribution function in energy-position space, a straightforward comparison of the numerical ab initio results with classical orbit theory is facilitated. Integration over position space yields directly the photoelectron spectra so that the various pathways contributing to a certain energy in the photoelectron spectra can be established in an unprecedented direct and transparent way.
The American Physical Society
2005
Article
http://edoc.mpg.de/249564
info:doi/10.1103/PhysRevLett.94.113001
Physical Review Letters, v.94, 1-4 (2005)
en
oai:edoc.mpg.de:2495702006-01-3137:954
Attosecond Probing of Vibrational Dynamics with High-Harmonic Generation
Lein, Manfred
expertsonly
The numerical solution of the time-dependent Schrödinger equation for vibrating hydrogen molecules in few-cycle laser pulses shows that high-harmonic generation is sensitive to the laser-induced vibrational motion. More intense harmonics are generated in heavier isotopes, the difference increasing with the harmonic frequency. Analytical theory reveals a dependence of the harmonics on the vibrational autocorrelation function. With the help of a genetic algorithm, the nuclear motion can be reconstructed from the harmonic spectra with sub-fs time resolution.
The American Physical Society
2005
Article
http://edoc.mpg.de/249570
info:doi/10.1103/PhysRevLett.94.053004
Physical Review Letters, v.94, 1-4 (2005)
en
oai:edoc.mpg.de:2496492006-08-1837:954
Radiative Corrections to Multi-Level Mollow-Type Spectra
Jentschura, Ulrich David
Evers, Jörg
Keitel, Christoph Helmut
This paper is concerned with two rather basic phenomena: the incoherent fluorescence spectrum of an atom driven by an intense laser field and the coupling of the atom to the (empty) modes of the radiation field. The sum of the many-photon processes gives rise to the inelastic part of the atomic fluorescence, which, for a two-level system, has a well-known characteristic three-peak structure that is known as the Mollow spectrum. From a theoretical point of view, the Mollow spectrum finds a natural interpretation in terms of transitions among laser-dressed states that are the energy eigenstates of a second-quantized two-level system strongly coupled to a driving laser field. As was recently shown, the quasi-energies of the laser-dressed states receive radiative corrections, which are nontrivially different from the results that one would expect from an investigation of the coupling of the bare states to the vacuum modes. In this article, we briefly review the basic elements required for an analysis of the dynamic radiative corrections, and we generalize the treatment of the radiative corrections to the incoherent part of the steady-state fluorescence to a three-level system consisting of 1S, 3P, and 2S states.
Article
http://edoc.mpg.de/249649
Laser Physics, v.15, 37-45
en
oai:edoc.mpg.de:2554112006-04-2637:954
Radiation spectra of laser-driven quantum relativistic electrons
Mocken, Guido Rudolf
Keitel, Christoph Helmut
expertsonly
A procedure to calculate the radiation spectrum emitted by an arbitrarily prepared Dirac wave packet is developed. It is based on the Dirac charge current and classical electrodynamic theory. Apart from giving absolute intensity values, it is exact in terms of relativistic retardation effects and angular dependence. We employ a laser driven free electron to demonstrate the advantages of our method as compared to traditional ones that merely rely on the Fourier transform of the dipole operator's expectation value. Classical reference calculations confirm the results obtained for the low-frequency part of the spectrum, especially in terms of the observed red-shifts, which clearly deviate from non-relativistic calculations. In the high-frequency part of the spectrum, we note appreciable deviations to the purely classical calculations which may be linked to quantum averaging effects.
Elsevier B.V.
2005
Article
http://edoc.mpg.de/255411
info:doi/10.1016/j.cpc.2004.12.002
Computer Physics Communications, v.166, 171-190 (2005)
en
oai:edoc.mpg.de:2554132006-04-2637:954
Above-threshold ionization beyond the dipole approximation
Klaiber, Michael
Hatsagortsyan, Karen Zaven
Keitel, Christoph Helmut
expertsonly
A generalization of the analytical theory of above-threshold ionization in the single active electron approximation is developed while taking into account leading non-dipole and relativistic corrections in the starting Hamiltonian. Special interest is placed on the high energy part of the photoelectron spectrum which consists of a plateau and a characteristic cutoff. It is shown that the correction due to the magnetic component of the laser field gives rise to a decrease of the plateau height, an increase of the maximal cutoff energy, and a drift of the emitted electrons in propagation direction of the laser field. Furthermore, the influence of the relativistic mass shift may become non-neglible by reducing the cutoff energy significantly. Spin effects or the Zitterbewegung play a comparably minor role in the investigated parameter regime of suboptical frequencies and high but not ultra-high laser intensities.
The American Physical Society
2005
Article
http://edoc.mpg.de/255413
info:doi/10.1103/PhysRevA.71.033408
Physical Review A, v.71, 1-7 (2005)
en
oai:edoc.mpg.de:2554162006-04-2637:954
Multiphoton quantum interference on a dipole-forbidden transition
Akram, Uzma
Evers, Jörg
Keitel, Christoph Helmut
expertsonly
We investigate the effect of an intense low-frequency field on the population decay of an excited two-level atom, where the two states are connected by a dipole-forbidden transition. In addition to the natural two-photon spontaneous decay, the low-frequency field gives rise to induced two-photon processes, where one of the two photons is spontaneous. Due to the low frequency of the applied field, the induced decay pathways may interfere with each other. We show how varying the parameters of the applied field allows switching between constructive and destructive interference, thereby increasing or decreasing the induced transition rate as compared to the rate without interference. As all relevant competing transitions are of the same multiphoton order, the system is a promising candidate to verify the idea of spontaneous-emission interference induced by multiphoton pathways experimentally.
© 2005 IOP Publishing Ltd
2005
Article
http://edoc.mpg.de/255416
info:doi/10.1088/0953-4075/38/4/L01
Journal of Physics B, v.38, L69-L77 (2005)
en
oai:edoc.mpg.de:2554232006-08-2137:954
Analytical Approach to Wave Packet Dynamics of Laser-Driven Particles beyond the Dipole Approximation
Verschl, Mario
Keitel, Christoph Helmut
expertsonly
An analytical approach to quantum mechanical wave packet dynamics of laser-driven particles is presented. The time-dependent Schroedinger equation is solved for an electron exposed to a linearly polarized plane wave of arbitrary shape. The calculation goes beyond the dipole approximation, such that magnetic field effects like wave packet shearing are included. Analytical expressions for the time-dependent widths of the wave packet and its orientation are established. These allow for a simple understanding of the wave packet dynamics.
2005
Article
http://edoc.mpg.de/255423
Laser Physics, v.15, 529-535 (2005)
en
oai:edoc.mpg.de:2554302006-08-2137:954
Some recent advances in bound-state quantum electrodynamics
Jentschura, Ulrich David
Evers, Jörg
expertsonly
We discuss recent progress in various problems related to bound-state quantum electrodynamics: the bound-electron g factor, two-loop self-energy corrections, and the laser-dressed Lamb shift. The progress relies on various advances in the bound-state formalism, including ideas inspired by effective field theories such as nonrelativistic quantum electrodynamics. Radiative corrections in dynamical processes represent a promising field for further investigations.
© 2005 NRC Canada
2005
Article
http://edoc.mpg.de/255430
info:doi/10.1139/P05-018
Canadian Journal of Physics, v.83, 375-386 (2005)
en
oai:edoc.mpg.de:2555672006-04-2737:954
Low-frequency-field-induced spontaneous-emission interference in a two-level atom placed in an anisotropic photonic crystal
Li, Gao-xiang
Evers, Jörg
Keitel, Christoph Helmut
expertsonly
We investigate the spontaneous-emission properties of a two-level atom embedded in a three-dimensional anisotropic photonic crystal. In addition to the modified density of states, the atom is driven by a coherent intense low-frequency field (LFF), which creates additional multiphoton decay channels with the exchange of two low-frequency photons and one spontaneous photon during an atomic transition. Due to the low frequency of the applied field, the various transition pathways may interfere with each other and thus give rise to a modified system dynamics. We find that even if all the atomic (bare and induced) transition frequencies are in the conducting band of the photonic crystal, there still may exist a photon–atom bound state in coexistence with propagating modes. The system also allows us to generate narrow lines in the spontaneous-emission spectrum. This spectrum is a function of the distance of the observer from the atom due to the band gap in the photonic crystal. The system properties depend on three characteristic frequencies, which are influenced by quantum interference effects. Thus these results can be attributed to a combination of interference and band-gap effects.
IOP Publ.
2005
Article
http://edoc.mpg.de/255567
urn:ISSN:0953-4075
Journal of Physics B-Atomic Molecular and Optical Physics, v.38, 1435-1451 (2005)
en
oai:edoc.mpg.de:2555772006-04-2737:954
Self-energy values for P states in hydrogen and low-Z hydrogenlike ions
Jentschura, Ulrich David
Mohr, Peter J.
expertsonly
We describe a nonperturbative (in Zalpha) numerical evaluation of the one-photon electron self-energy for 3P1/2, 3P3/2, 4P1/2, and 4P3/2 states in hydrogenlike atomic systems with charge numbers Z=1 to 5. The numerical results are found to be in agreement with known terms in the expansion of the self-energy in powers of Zalpha and lead to improved theoretical predictions for the self-energy shift of these states.
©2005 The American Physical Society
2005
Article
http://edoc.mpg.de/255577
urn:ISSN:1050-2947
Physical Review A, v.72, 1-3 (2005)
en
oai:edoc.mpg.de:2557852006-04-2737:954
Calculation of hydrogenic Bethe logarithms for Rydberg states
Jentschura, Ulrich David
Mohr, Peter J.
expertsonly
We describe the calculation of hydrogenic (one-loop) Bethe logarithms for all states with principal quantum numbers n<=200. While, in principle, the calculation of the Bethe logarithm is a rather easy computational problem involving only the nonrelativistic (Schrödinger) theory of the hydrogen atom, certain calculational difficulties affect highly excited states, and in particular states for which the principal quantum number is much larger than the orbital angular momentum quantum number. Two evaluation methods are contrasted. One of these is based on the calculation of the principal value of a specific integral over a virtual photon energy. The other method relies directly on the spectral representation of the Schrödinger–Coulomb propagator. Selected numerical results are presented. The full set of values is available at arXiv.org/quant-ph/0504002.
APS
2005
Article
http://edoc.mpg.de/255785
urn:ISSN:1050-2947
Physical Review A, v.72, 1-9 (2005)
en
oai:edoc.mpg.de:2557872006-04-2737:954
Thin crystal layers in superstrong laser fields: Dynamics and coherent x-ray generation
Hatsagortsyan, Karen Zaven
Keitel, Christoph Helmut
expertsonly
Coherent x-ray generation is investigated for a thin solid layer or any other periodic atomic structure with limited dimensions exposed to a short, superintense laser pulse. We single out a selective range of parameters at which the impact of nonlinear collective processes on ion dynamics is reduced. This allows us to consider an ionic structure that is quasiregular during the brief interaction, which we prove also by particle-in-cell simulations. In the relativistic regimes of the interaction, when the transversal oscillation amplitude of the electron in the laser field exceeds the layer transversal width, the multiphoton scattering of electrons dominates over recombination to bound states. Electrons accelerated by the laser field penetrate through the periodic ionic structure, emitting coherent bremsstrahlung. Hard x rays are shown to amplify along the interaction length due to stimulated coherent bremsstrahlung. The high gain of the scheme compensates for the short interaction length, yielding a gain-length product competitive with other coherent x-ray sources. Limitations on the gain due to the energy spread of the electrons and the short time of the interaction are estimated.
APS
2005
Article
http://edoc.mpg.de/255787
urn:ISSN:1050-2947
Physical Review A, v.72, 1-15 (2005)
en
oai:edoc.mpg.de:2557882006-04-2737:954
Strong-field approximation for intense-laser-atom processes: The choice of gauge
Bauer, Dieter
Milosevic, D. B.
Becker, W.
expertsonly
The strong-field approximation (SFA) can be and has been applied in both length gauge and velocity gauge with quantitatively conflicting answers. For ionization of negative ions with a ground state of odd parity, the predictions of the two gauges differ qualitatively: in the envelope of the angular-resolved energy spectrum, dips in one gauge correspond to humps in the other. We show that the length-gauge SFA matches the exact numerical solution of the time-dependent Schrödinger equation.
APS
2005
Article
http://edoc.mpg.de/255788
urn:ISSN:1050-2947
Physical Review A, v.72, 1-5 (2005)
en
oai:edoc.mpg.de:2557892006-04-2737:954
Renormalization-group analysis of layered sine-Gordon type models
Nandori, István
Nagy, S.
Sailer, K.
Jentschura, Ulrich David
expertsonly
renormalization group evolution of parameters; renormalization
We analyze the phase structure and the renormalization group (RG) flow of the generalized sine-Gordon models with nonvanishing mass terms, using the Wegner–Houghton RG method in the local potential approximation. Particular emphasis is laid upon the layered sine-Gordon (LSG) model, which is the bosonized version of the multi-flavour Schwinger model and approaches the sum of two “normal”, massless sine-Gordon (SG) models in the limit of a vanishing interlayer coupling J. Another model of interest is the massive sine-Gordon (MSG) model. The leading-order approximation to the UV (ultraviolet) RG flow predicts two phases for the LSG as well as for the MSG, just as it would be expected for the SG model, where the two phases are known to be separated by the Coleman fixed point. The presence of finite mass terms (for the LSG and the MSG) leads to corrections to the UV RG flow, which are naturally identified as the “mass corrections”. The leading-order mass corrections are shown to have the following consequences: (i) for the MSG model, only one phase persists, and (ii) for the LSG model, the transition temperature is modified. Within the mass-corrected UV scaling laws, the limit of J→0 is thus nonuniform with respect to the phase structure of the model. The modified phase structure of general massive sine-Gordon models is connected with the breaking of symmetries in the internal space spanned by the field variables. For the LSG, the second-order subleading mass corrections suggest that there exists a cross-over regime before the IR scaling sets in, and the nonlinear terms show explicitly that higher-order Fourier modes appear in the periodic blocked potential.
Elsevier
2005
Article
http://edoc.mpg.de/255789
urn:ISSN:0550-3213
Nuclear Physics B, v.725, 467-492 (2005)
en
oai:edoc.mpg.de:2559722006-04-2737:954
Techniques in analytic Lamb shift calculations
Jentschura, Ulrich David
expertsonly
quantum electrodynamics; bound states; atomic physics
Quantum electrodynamics has been the first theory to emerge from the ideas of regularization and renormalization, and the coupling of the fermions to the virtual excitations of the electromagnetic field. Today, bound-state quantum electrodynamics provides us with accurate theoretical predictions for the transition energies relevant to simple atomic systems, and steady theoretical progress relies on advances in calculational techniques, as well as numerical algorithms. In this brief review, we discuss one particular aspect connected with the recent progress: the evaluation of relativistic corrections to the one-loop bound-state self-energy in a hydrogenlike ion of low nuclear charge number, for excited non-S states, up to the order of alpha (Zalpha)^6 in units of the electron mass. A few details of calculations formerly reported in the literature are discussed, and results for 6F, 7F, 6G and 7G states are given.
2005
Article
http://edoc.mpg.de/255972
urn:ISSN:0217-7323
Modern Physics Letters A, v.20, 2261-2276 (2005)
en
oai:edoc.mpg.de:2559732006-04-2737:954
Isospin dependence in the odd-even staggering of nuclear binding energies
Litvinov, Y. A.
Burvenich, Thomas Josef
Geissel, H.
Novikov, Y. N.
Patyk, Z.
Scheidenberger, C.
Attallah, F.
Audi, G.
Beckert, K.
Bosch, F.
Falch, M.
Franzke, B.
Hausmann, M.
Kerscher, T.
Klepper, O.
Kluge, H. J.
Kozhuharov, C.
Lobner, K. E. G.
Madland, D. G.
Maruhn, J. A.
Munzenberg, G.
Nolden, F.
Radon, T.
Steck, M.
Typel, S.
Wollnik, H.
expertsonly
The FRS-ESR facility at GSI provides unique conditions for precision measurements of large areas on the nuclear mass surface in a single experiment. Values for masses of 604 neutron-deficient nuclides (30<=Z<=92) were obtained with a typical uncertainty of 30 µu. The masses of 114 nuclides were determined for the first time. The odd-even staggering (OES) of nuclear masses was systematically investigated for isotopic chains between the proton shell closures at Z=50 and Z=82. The results were compared with predictions of modern nuclear models. The comparison revealed that the measured trend of OES is not reproduced by the theories fitted to masses only. The spectral pairing gaps extracted from models adjusted to both masses, and density related observables of nuclei agree better with the experimental data.
The American Physical Society
2005
Article
http://edoc.mpg.de/255973
urn:ISSN:0031-9007
Physical Review Letters, v.95, 1-4 (2005)
en
oai:edoc.mpg.de:2559822006-04-2737:954
Rapid refractive index enhancements via laser-mediated collectivity
Macovei, Mihai
Keitel, Christoph Helmut
expertsonly
The collective interaction via the environmental vacuum is investigated for a mixture of two different multi-atom ensembles in a moderately intense laser field. Due to the numerous inter-atomic couplings, the laser-dressed system may react sensitively and rapidly with respect to changes in the atomic and laser parameters. We show for weak probe fields that in the absence of absorption both the index of refraction and the group velocity may be modified strongly and rapidly due to the collectivity.
IOP
2005
Article
http://edoc.mpg.de/255982
urn:ISSN:0953-4075
Journal of Physics B-Atomic Molecular and Optical Physics, v.38, L315-L321 (2005)
en
oai:edoc.mpg.de:2559982006-04-2737:954
Attosecond double-slit experiment
Lindner, F.
Schatzel, M. G.
Walther, H.
Baltuska, A.
Goulielmakis, E.
Krausz, F.
Milosevic, D. B.
Bauer, Dieter
Becker, W.
Paulus, G. G.
expertsonly
A new scheme for a double-slit experiment in the time domain is presented. Phase-stabilized few-cycle laser pulses open one to two windows (slits) of attosecond duration for photoionization. Fringes in the angle-resolved energy spectrum of varying visibility depending on the degree of which-way information are measured. A situation in which one and the same electron encounters a single and a double slit at the same time is observed. The investigation of the fringes makes possible interferometry on the attosecond time scale. From the number of visible fringes, for example, one derives that the slits are extended over about 500 as.
The American Physical Society
2005
Article
http://edoc.mpg.de/255998
urn:ISSN:0031-9007
Physical Review Letters, v.95, 1-4 (2005)
en
oai:edoc.mpg.de:2560032006-04-2737:954
Complete two-loop correction to the bound-electron g factor
Pachucki, K.
Czarnecki, A.
Jentschura, Ulrich David
Yerokhin, Vladimir A.
expertsonly
Within a systematic approach based on dimensionally regularized nonrelativistic quantum electrodynamics, we derive a complete result for the two-loop correction to order (alpha/pi)2(Zalpha)4 for the g factor of an electron bound in an nS state of a hydrogenlike ion. The results obtained significantly improve the accuracy of the theoretical predictions for the hydrogenlike carbon and oxygen ions and influence the value of the electron mass inferred from g-factor measurements.
The American Physical Society
2005
Article
http://edoc.mpg.de/256003
urn:ISSN:1050-2947
Physical Review A, v.72, 1-11 (2005)
en
oai:edoc.mpg.de:2566542006-04-2737:954
Precise calculation of transition frequencies of hydrogen and deuterium based on a least-squares analysis
Jentschura, Ulrich David
Kotochigova, Svetlana
Le Bigot, Eric-Olivier
Mohr, Peter J.
Taylor, Barry N.
expertsonly
We combine a limited number of accurately measured transition frequencies in hydrogen and deuterium, recent quantum electrodynamics (QED) calculations, and, as an essential additional ingredient, a generalized least-squares analysis, to obtain precise and optimal predictions for hydrogen and deuterium transition frequencies. Some of the predicted transition frequencies have relative uncertainties more than an order of magnitude smaller than that of the g factor of the electron, which was previously the most accurate prediction of QED.
The American Physical Society
2005
Article
http://edoc.mpg.de/256654
urn:ISSN:0031-9007
Physical Review Letters, v.95, 1-4 (2005)
en
oai:edoc.mpg.de:2566562006-04-2737:954
Calculation of the one- and two-loop lamb shift for arbitrary excited hydrogenic states
Czarnecki, A.
Jentschura, Ulrich David
Pachucki, K.
expertsonly
General expressions for quantum electrodynamic corrections to the one-loop self-energy [of order alpha(Zalpha)6] and for the two-loop Lamb shift [of order alpha2(Zalpha)6] are derived. The latter includes all diagrams with closed fermion loops. The general results are valid for arbitrary excited non-S hydrogenic states and for the normalized Lamb shift difference of S states, defined as Deltan=n3DeltaE(nS)-DeltaE(1S). We present numerical results for one-loop and two-loop corrections for excited S, P, and D states. In particular, the normalized Lamb shift difference of S states is calculated with an uncertainty of order 0.1 kHz.
The American Physical Society
2005
Article
http://edoc.mpg.de/256656
urn:ISSN:0031-9007
Physical Review Letters, v.95, 1-4 (2005)
en
oai:edoc.mpg.de:2566622006-05-0237:954
Laser-dressed vacuum polarization in a Coulomb field
Milstein, Alexander I.
Terekhov, Ivan S.
Jentschura, Ulrich David
Keitel, Christoph Helmut
expertsonly
We investigate quantum electrodynamic effects under the influence of an external, time-dependent electromagnetic field, which mediates dynamic modifications of the radiative corrections. Specifically, we consider the quantum electrodynamic vacuum-polarization tensor under the influence of two external background fields: a strong laser field and a nuclear Coulomb field. We calculate the charge and current densities induced by a nuclear Coulomb field in the presence of a laser field. We find the corresponding induced scalar and vector potentials. The induced potential, in first-order perturbation theory, leads to a correction to atomic energy levels. The external laser field breaks the rotational symmetry of the system. Consequently, the induced charge density is not spherically symmetric, and the energy correction therefore leads to a "polarized Lamb shift." In particular, the laser generates an additional potential with a quadrupole moment. The corresponding laser-dressed vacuum-polarization potential behaves like 1/r3 at large distances, unlike the Uehling potential, which vanishes exponentially for large r. The energy corrections are of the same order of magnitude for hydrogenic levels, irrespective of the angular momentum quantum number. The induced current leads to a transition dipole moment which oscillates at the second harmonic of the laser frequency and is mediated by second-order harmonic generation in the vacuum-polarization loop. In the far field, at distances r>>1/omega from the nucleus (omega is the laser frequency), the laser induces mutually perpendicular electric and magnetic fields, which give rise to an energy flux that corresponds to photon fusion leading to the generation of real photons, again at the second harmonic of the laser. Our investigation might be useful for other situations where quantum field theoretic phenomena are subjected to external fields of a rather involved structure.
©2005 The American Physical Society
2005
Article
http://edoc.mpg.de/256662
urn:ISSN:1050-2947
Physical Review A, v.72, 1-12 (2005)
en
oai:edoc.mpg.de:2566652006-05-0237:954
Relativistic electron correlation, quantum electrodynamics, and the lifetime of the 1s(2)2s(2)2p P-2(3/2)o level in boronlike argon
Lapierre, Alain
Jentschura, Ulrich David
Crespo Lopez-Urrutia, José R.
Braun, Johannes
Brenner, Günter
Bruhns, Hjalmar
Fischer, Daniel
Gonzalez Martinez, Antonio J.
Harman, Zoltan
Johnson, W. R.
Keitel, Christoph Helmut
Mironov, Vladimir
Osborne, Christopher J.
Sikler, Günter
Soria Orts, Rosario
Shabaev, V.
Tawara, Hiroyuki
Tupitsyn, Ilya I.
Ullrich, Joachim
Volotka, A.
expertsonly
The lifetime of the Ar13+ 1s22s22p 2P3/2o metastable level was determined at the Heidelberg Electron Beam Ion Trap to be 9.573(4)(5) ms(stat)(syst). The accuracy level of one per thousand makes this measurement sensitive to quantum electrodynamic effects like the electron anomalous magnetic moment (EAMM) and to relativistic electron-electron correlation effects like the frequency-dependent Breit interaction. Theoretical predictions, adjusted for the EAMM, cluster about a lifetime that is approximately 3sigma shorter than our experimental result.
©2005 The American Physical Society
2005
Article
http://edoc.mpg.de/256665
urn:ISSN:0031-9007
Physical Review Letters, v.95, 1-4 (2005)
en
oai:edoc.mpg.de:2566722006-05-0237:954
Harmonic generation from laser-driven vacuum
Di Piazza, Antonino
Hatsagortsyan, Karen Zaven
Keitel, Christoph Helmut
notspecified
We investigate the feasibility that, in the field of a superstrong standing laser wave, high-order harmonics of the pumping laser are generated from vacuum. Analytical calculations employing adiabatic perturbation theory show that, for laser electric fields larger than Ecr=m2c3/[h-bar]e=1.3×1016 V/cm, high-order harmonics are generated. The harmonic spectrum shows a wide plateau followed by a cutoff. The cutoff starts approximately at photon energies [h-bar]omegaM~sqrt([h-bar]ecE[sub L]), with EL being the amplitude of the laser field. In the opposite limit EL<<Ecr, the emission of high harmonics is very unlikely. In this case, a feasibility analysis for the experimental observation of the photon-photon scattering process using x-ray free electron lasers shows that the requirements are much less restrictive than those required to observe electron-positron pair creation.
©2005 The American Physical Society
2005
Article
http://edoc.mpg.de/256672
urn:ISSN:1550-7998
Physical Review D, v.72, 1-23 (2005)
en
oai:edoc.mpg.de:2566732006-08-2137:954
Free-electron quantum signatures in intense laser fields
Mahmoudi, Mohammad
Salamin, Yousef I.
Keitel, Christoph Helmut
expertsonly
Quantum signatures of a free electron in interaction with a continuous-wave radiation field are investigated by looking for negativities in the Wigner function of the system. The free-electron wave function in the radiation field is calculated fully analytically by solving the appropriate Schrödinger equation in the Krammers-Henneberger frame. It is found that pronounced quantum signatures show up already for a laser peak field of magnitude E0=1–2 a.u. and a frequency omega=1 a.u. However, the nonclassical behavior gets lost if the interaction with the radiation field is taken in the dipole approximation.
©2005 The American Physical Society
2005
Article
http://edoc.mpg.de/256673
urn:ISSN:1050-2947
Physical Review A, v.72, 1-7 (2005)
en
oai:edoc.mpg.de:2566752006-03-2037:954
Phase-dependent interference mechanisms in a three-level Lambda system driven by a quantized laser field
Evers, Jörg
notspecified
The dynamics of an atomic few-level system can depend on the phase of driving fields coupled to the atom if certain conditions are satisfied. This is of particular interest to control interference effects, which can alter the system properties considerably. In this article, we discuss the mechanisms of such phase control and interference effects in an atomic three-level system in the ? configuration, where the upper state spontaneously decays into the two lower states. The lower states are coupled by a driving field, which we treat as quantized. This allows for an interpretation on the single photon level for both the vacuum and the driving field. By analysing the system behaviour for a driving field initially in non-classical states with only a few Fock number states populated, we find that even though the driving field is coupled to the lower states only, it induces a multiplet of upper states. Then interference occurs independently in three-level subsystems in the V configuration, each formed by two adjacent upper states and a single dressed lower state.
© 2005 Taylor & Francis
2005
Article
http://edoc.mpg.de/256675
urn:ISSN:0950-0340
Journal of Modern Optics, v.52, 2699-2712 (2005)
en
oai:edoc.mpg.de:2566772006-05-0237:954
Mechanisms of ultrahigh-order harmonic generation
Lein, Manfred
expertsonly
We analyze mechanisms of high-order harmonic generation from two-center molecules at large internuclear separations in linearly polarized laser fields. Since laser-driven electrons acquire instantaneous kinetic energies of up to 8 times the ponderomotive potential Up, recombination at an appropriately placed nucleus leads to ultrahigh-order harmonic emission [P. Moreno, L. Plaja, and L. Roso, Phys. Rev. A 55, R1593 (1997)]. By solving the time-dependent Schrödinger equation for model systems, we show that this mechanism is only efficient if the single-particle orbital of the electron is coherently delocalized over the two potential wells. This is realized in the ground state of a one-electron molecular ion. In a neutral molecule or in a molecular ion created by ionization of a neutral molecule at large internuclear distance, the coherence is destroyed by electron-electron correlation.
©2005 The American Physical Society
2005
Article
http://edoc.mpg.de/256677
urn:ISSN:1050-2947
Physical Review A, v.72, 1-4 (2005)
en
oai:edoc.mpg.de:2566782006-05-0237:954
Quantum correlations of an atomic ensemble via an incoherent bath
Macovei, Mihai
Evers, Jörg
Keitel, Christoph Helmut
notspecified
A rich variety of quantum features can be found in a collection of atoms driven only by an incoherent bath. To demonstrate this, we discuss a sample of three-level atoms in ladder configuration interacting via the surrounding bath, and show that the fluorescence light emitted by this system exhibits nonclassical properties. Realizations could be thermal baths for microwave transitions, or incoherent broadband fields for optical transitions. In a small sample of atoms, the emitted light can be switched from sub- to super-Poissonian and from antibunching to superbunching controlled by the mean number of atoms in the sample. Larger samples allow us to generate superbunched light over a wide range of bath parameters and thus fluorescence light intensities. We also identify parameter ranges where the fields emitted on the two transitions are strongly correlated or anticorrelated, such that the Cauchy-Schwarz inequality is violated. As in a moderately strong bath this violation occurs also for larger numbers of atoms, such samples exhibit macroscopic quantum effects.
©2005 The American Physical Society
2005
Article
http://edoc.mpg.de/256678
urn:ISSN:1050-2947
Physical Review A, v.72, 1-5 (2005)
en
oai:edoc.mpg.de:2566802008-03-0337:954
Comparison of classical and second quantized description of the dynamic Stark shift
Haas, Martin
Jentschura, Ulrich David
Keitel, Christoph Helmut
notspecified
We compare the derivation of the dynamic Stark shift of hydrogenic energy levels in a classical framework with an adiabatically damped laser-atom interaction, which is equivalent to the Gell-Mann-Low-Sucher formula, and a treatment based on time-independent perturbation theory, with a second-quantized laser-atom dipole interaction Hamiltonian. Our analysis applies to a laser that excites a two-photon transition in atomic hydrogen or in a hydrogenlike ion with low nuclear charge number. Our comparisons serve to demonstrate why the dynamic Stark shift may be interpreted as a stimulated radiative correction and illustrates connections between the two derivations. The simplest of the derivations is the fully quantized approach. The classical and the second-quantized treatment are shown to be equivalent in the limit of large photon numbers.
©2006 American Association of Physics Teachers
2006
Article
http://edoc.mpg.de/256680
urn:ISSN:0002-9505
American Journal of Physics, v.74, 77-81 (2006)
en
oai:edoc.mpg.de:2566832006-05-0337:954
High-order harmonic generation in vibrating molecules
Chirila, Ciprian C.
Lein, Manfred
expertsonly
The generation of high-order harmonics in small diatomic molecules is theoretically investigated with inclusion of the vibrational degree of freedom. The results obtained from the solution of the time-dependent Schrödinger equation for a model H2 molecule are interpreted by analysing the influence of the vibrational motion in the framework of the strong-field approximation. Ionization launches a vibrational wave packet whose motion is correlated with the motion of the continuum electron wave packet. The harmonics are sensitive to a correlation function quantifying the overlap between the vibrational wave packet at the time of recombination and a vibrational target wave packet, i.e. the wave packet for which de-excitation into the ground state is most likely. We show that more intense harmonics are generated in heavier isotopes due to the slower nuclear motion.
2006
Article
http://edoc.mpg.de/256683
info:doi/10.1080/09500340500233636
Journal of Modern Optics, v.53, 113-124 (2006)
en
oai:edoc.mpg.de:2566842007-09-1937:954
Quantum-orbit theory of high-order atomic processes in intense laser fields
Milosevic, D. B.
Bauer, Dieter
Becker, W.
expertsonly
The quantum-orbit formalism of high-order atomic processes in a strong laser field is presented starting from the strong-field approximation generalized to include higher-order effects. It is shown how to apply the quantum-orbit theory to various processes such as high-order above-threshold ionization and detachment, high-order harmonic generation, laser-assisted X-ray–atom scattering, laser-assisted electron–ion recombination, laser-assisted electron–atom scattering and non-sequential double ionization. Particular attention is devoted to high-order above-threshold ionization by few-cycle laser pulses. The results obtained using the strong-field approximation and the theory of quantum orbits are compared with the ab initio solution of the time-dependent Schrödinger equation. It is shown that Coulomb effects are important for low-energy electron spectra.
2006
Article
http://edoc.mpg.de/256684
info:doi/10.1080/09500340500186099
Journal of Modern Optics, v.53, 125-134 (2006)
en
oai:edoc.mpg.de:2566912006-05-0337:954
Quantum Interference Enforced by Time-Energy Complementarity
Kiffner, Martin
Evers, Jörg
Keitel, Christoph Helmut
expertsonly
The interplay of the concepts of complementarity and interference in the time-energy domain are studied. In particular, we theoretically investigate the fluorescence light from a J=1/2 to J=1/2 transition that is driven by a monochromatic laser field. We find that the spectrum of resonance fluorescence exhibits a signature of vacuum-mediated interference effects, whereas the total intensity is not affected by interference. We demonstrate that this result is a consequence of the principle of complementarity, applied to time and energy. Since the considered level scheme can be found, e.g., in 198Hg+ ions, our model system turns out to be an ideal candidate to provide evidence for as yet experimentally unconfirmed vacuum-induced atomic coherences.
©2006 The American Physical Society
2006
Article
http://edoc.mpg.de/256691
info:doi/10.1103/PhysRevLett.96.100403
Physical Review Letters, v.96, 1-4 (2006)
en
oai:edoc.mpg.de:2567202007-09-1937:954
On the validity of the strong field approximation and simple man's theory
Bauer, Dieter
Milosevic, D. B.
Becker, W.
expertsonly
Few-cycle above-threshold ionization spectra of atomic hydrogen, calculated via the numerical solution of the time-dependent Schrödinger equation (TDSE), are compared with those predicted by the strong field approximation. Good agreement is obtained for the energetic, rescattered photoelectrons whereas the low-energy part of the electron spectra differ significantly. The latter disagreement is shown to originate from the long-range character of the Coulomb potential. In the second part of the paper a novel quantum distribution function is introduced, which facilitates a direct comparison of the classical electron orbits used in simple man's theory with the exact numerical TDSE result. It is shown that well localized electron wave packets emerge, oriented along the simple man's classical trajectories as the energy resolution in the quantum distribution function is reduced.
© 2006 Taylor & Francis
2006
Article
http://edoc.mpg.de/256720
info:doi/10.1080/09500340500217258
Journal of Modern Optics, v.53, 135-147 (2006)
en
oai:edoc.mpg.de:2570752006-05-0337:954
Measurement of the separation between atoms beyond diffraction limit
Chang, Jun Tao
Evers, Jörg
Scully, Marlan Orvil
Zubairy, Muhammad Suhail
expertsonly
Precision measurement of small separations between two atoms or molecules has been of interest since the early days of science. Here, we discuss a scheme which yields spatial information on a system of two identical atoms placed in a standing wave laser field. The information is extracted from the collective resonance fluorescence spectrum, relying entirely on far-field imaging techniques. Both the interatomic separation and the positions of the two particles can be measured with fractional-wavelength precision over a wide range of distances from about λ/550 to λ/2.
©2006 The American Physical Society
2006
Article
http://edoc.mpg.de/257075
info:doi/10.1103/PhysRevA.73.031803
Physical Review A, v.73, 1-4 (2006)
en
oai:edoc.mpg.de:2846472007-09-1837:954
Above-threshold ionization by few-cycle pulses
Milosevic, D. B.
Paulus, G. G.
Bauer, D.
Becker, W.
expertsonly
The theoretical description and the experimental methods and results for above-threshold ionization (ATI) by few-cycle pulses are reviewed. A pulse is referred to as a few-cycle pulse if its detailed shape, parametrized by its carrier-envelope phase, affects its interaction with matter. Angular-resolved ATI spectra are analysed with the customary strong-field approximation (SFA) as well as the numerical solution of the time-dependent Schrödinger equation (TDSE). After a general discussion of the characteristics and the description of few-cycle pulses, the behaviour of the ATI spectrum under spatial inversion is related to the shape of the laser field. The ATI spectrum both for the direct and for the rescattered electrons in the context of the SFA is evaluated by numerical integration and by the method of steepest descent (saddle-point integration), and the results are compared. The saddle-point method is modified to avoid the singularity of the dipole transition matrix element at the steepest-descent times. With the help of the saddle-point method and its classical limit, namely the simple-man model, the various features of the ATI spectrum, their behaviour under inversion, the cut-offs and the presence or absence of ATI peaks are analysed as a function of the carrier-envelope phase of the few-cycle laser field. All features observed in the spectra can be explained in terms of a few quantum orbits and their superposition. The validity of the SFA and the concept of quantum orbits are established by comparing the ATI spectra with those obtained numerically from the ab initio solution of the TDSE.
© 2006 IOP Publishing Ltd
2006
Article
http://edoc.mpg.de/284647
info:doi/10.1088/0953-4075/39/14/R01
Journal of Physics B: Atomic, Molecular and Optical Physics, v.39, R203-R262 (2006)
en
oai:edoc.mpg.de:2848002008-03-0337:954
Mass measurements and the bound-electron g factor
Jentschura, Ulrich David
Czarnecki, A.
Pachucki, K.
Yerokhin, Vladimir
expertsonly
The accurate determination of atomic masses and the high-precision measurement of the bound-electron g factor are prerequisites for the determination of the electron mass, which is one of the fundamental constants of nature. In the 2002 CODATA adjustment [P.J. Mohr, B.N. Taylor, Rev. Mod. Phys. 77 (2005) 1], the values of the electron mass and the electron–proton mass ratio are mainly based on g factor measurements in combination with atomic mass measurements. In this paper, we briefly discuss the prospects for obtaining other fundamental information from bound-electron g factor measurements, we present some details of a recent investigation of two-loop binding corrections to the g factor, and we also investigate the radiative corrections in the limit of highly excited Rydberg S states with a long lifetime, where the g factor might be explored using a double resonance experiment.
© 2006 Elsevier B.V.
2006
Article
http://edoc.mpg.de/284800
info:doi/10.1016/j.ijms.2005.12.051
International Journal of Mass Spectrometry, v.251, 102-108 (2006)
en
oai:edoc.mpg.de:2848022006-08-1737:954
Collective coherent population trapping in a thermal field
Macovei, Mihai
Ficek, Zbigniew
Keitel, Christoph Helmut
expertsonly
We analyze the efficiency of coherent population trapping (CPT) in a superposition of the ground states of three-level atoms under the influence of the decoherence process induced by a broadband thermal field. We show that in a single atom there is no perfect CPT when the atomic transitions are affected by the thermal field. The perfect CPT may occur when only one of the two atomic transitions is affected by the thermal field. In the case when both atomic transitions are affected by the thermal field, we demonstrate that regardless of the intensity of the thermal field the destructive effect on the CPT can be circumvented by the collective behavior of the atoms. An analytic expression was obtained for the populations of the upper atomic levels which can be considered as a measure of the level of thermal decoherence. The results show that the collective interaction between the atoms can significantly enhance the population trapping in that the population of the upper state decreases with an increased number of atoms. The physical origin of this feature is explained by the semiclassical dressed-atom model of the system. We introduce the concept of multiatom collective coherent population trapping by demonstrating the existence of collective (entangled) states whose storage capacity is larger than that of the equivalent states of independent atoms.
©2006 The American Physical Society
2006
Article
http://edoc.mpg.de/284802
info:doi/10.1103/PhysRevA.73.063821
Physical Review A, v.73 (2006)
en
oai:edoc.mpg.de:2848072006-08-1737:954
Interference in the resonance fluorescence of two incoherently coupled transitions
Kiffner, Martin
Evers, Jörg
Keitel, Christoph Helmut
expertsonly
The fluorescence light emitted by a four-level system in J=1/2 to J=1/2 configuration driven by a monochromatic laser field and in an external magnetic field is studied. We show that the spectrum of resonance fluorescence emitted on the transitions shows a signature of spontaneously generated interference effects. The degree of interference in the fluorescence spectrum can be controlled by means of the external magnetic field, provided that the Landé g factors of the excited and the ground state doublet are different. For a suitably chosen magnetic field strength, the relative weight of the Rayleigh line can be completely suppressed, even for low intensities of the coherent driving field. The incoherent fluorescence spectrum emitted on the transitions exhibits a very narrow peak whose width and weight depend on the magnetic field strength. We demonstrate that the spectrum of resonance fluorescence emitted on the transitions shows an indirect signature of interference. A measurement of the relative peak heights in the spectrum from the transitions allows us to determine the branching ratio of the spontaneous decay of each excited state into the channel.
©2006 The American Physical Society
2006
Article
http://edoc.mpg.de/284807
info:doi/10.1103/PhysRevA.73.063814
Physical Review A, v.73 (2006)
en
oai:edoc.mpg.de:2848082008-03-0337:954
Quantum electrodynamic corrections to the hyperfine structure of excited S states
Jentschura, Ulrich David
Yerokhin, Vladimir A.
expertsonly
State-dependent quantum electrodynamic corrections are evaluated for the hyperfine splitting of nS states for arbitrary principal quantum number n. The calculations comprise both the self-energy and the vacuum-polarization correction of order (Z)2EF and the recoil correction of order (Z)2(m/M)EF. Higher-order corrections are summarized and partly reevaluated as well. Accurate predictions for hydrogen hyperfine splitting intervals of nS states with n=2,,8 are presented. The results obtained are important due to steady progress in hydrogen spectroscopy for transitions involving highly excited S states.
©2006 The American Physical Society
2006
Article
http://edoc.mpg.de/284808
info:doi/10.1103/PhysRevA.73.062503
Physical Review A, v.73 (2006)
en
oai:edoc.mpg.de:2848102006-08-1737:954
Polarization-operator approach to electron-positron pair production in combined laser and Coulomb fields
Milstein, Alexander I.
Müller, Carsten
Hatsagortsyan, Karen Zaven
Jentschura, Ulrich David
Keitel, Christoph Helmut
expertsonly
The optical theorem is applied to the process of electron-positron pair creation in the superposition of a nuclear Coulomb and a strong laser field. We derive representations for the total production rate as twofold integrals, both for circular laser polarization and for the general case of elliptic polarization. Our approach allows us to obtain, by analytical means, the asymptotic behavior of the pair creation rate for various limits of interest. In particular, we consider pair production by two-photon absorption and show that, close to the energetic threshold of this process, the rate obeys a power law in the laser frequency with different exponents for linear and circular laser polarization. With the help of the upcoming x-ray laser sources, our results could be tested experimentally.
©2006 The American Physical Society
2006
Article
http://edoc.mpg.de/284810
info:doi/10.1103/PhysRevA.73.062106
Physical Review A, v.73 (2006)
en
oai:edoc.mpg.de:2848112006-08-1737:954
Gauge-invariant relativistic strong-field approximation
Klaiber, Michael
Hatsagortsyan, Karen Zaven
Keitel, Christoph Helmut
expertsonly
The problem of the choice of gauge in the relativistic strong-field approximation (SFA) is analyzed. The main motivation is to obtain a relativistic ionization amplitude in the SFA which in the nonrelativistic limit coincides with the conventional well-accepted results of the SFA in the length gauge. A gauge-invariant formulation of the SFA is derived which is applicable both in the nonrelativistic as well as in the relativistic regime of laser-induced strong-field ionization phenomena. The gauge invariance is achieved by means of employment of an eigenstate of the physical energy operator for the initial atomic state. As an example, a comparison of predictions of the gauge-invariant theory with conventional SFA results in the radiation gauge is given for above-threshold ionization in the relativistic regime.
©2006 The American Physical Society
2006
Article
http://edoc.mpg.de/284811
Physical Review A, v.73 (2006)
en
oai:edoc.mpg.de:2848142010-05-2537:954
Two-photon excitation dynamics in bound two-body Coulomb systems including ac Stark shift and ionization
Haas, Martin
Jentschura, Ulrich David
Keitel, Christoph Helmut
Kolachevsky, N.
Herrmann, M.
Fendel, P.
Fischer, M.
Udem, Thomas
Holzwarth, R.
Hänsch, T. W.
Scully, M. O.
Agarwal, G. S.
expertsonly
One of the dominant systematic effects that shift resonance lines in high-precision measurements of two-photon transitions is the dynamic (ac) Stark shift. For suitable laser frequencies, the ac Stark shift acquires an imaginary part which corresponds to the rate of resonant one-photon ionization of electrons into a continuum state. At the current level of spectroscopic accuracy, the underlying time-dependent quantum dynamics governing the atomic two-photon excitation process must be well understood, and related considerations are the subject of the present paper. In order to illustrate the basic mechanisms in the transient regime, we investigate an analytically solvable model scenario for the population dynamics in the density matrix formalism and describe in detail how to generalize the corresponding equations of motion for individual experimental use. We also calculate the dynamic Stark shift for two-photon S-S and S-D transitions in bound two-body Coulomb systems and the corresponding two-photon transition matrix elements. In particular, we investigate transitions for which the 1S ground state or alternatively the metastable 2S state acts as the lower-energy state, and for which states with n20 represent the upper states. Relativistic and radiative corrections to the excitation dynamics, and the corresponding limitations to the accuracy of the measurements, are briefly discussed. Our considerations suggest the general feasibility of a detection mechanism, offering high quantum efficiency, based on two-step three-photon resonant ionization spectroscopy, for large classes of experimentally relevant two-photon transitions in two-body Coulomb systems.
©2006 The American Physical Society
2006
Article
http://edoc.mpg.de/284814
info:doi/10.1103/PhysRevA.73.052501
Physical Review A, v.73 (2006)
en
oai:edoc.mpg.de:2848152008-03-0337:954
Anomalous magnetic moments of free and bound leptons
Czarnecki, A.
Jentschura, Ulrich David
Pachucki, K.
Yerokhin, Vladimir
expertsonly
We review the theoretical knowledge of anomalous magnetic moments of free electrons and muons, and of electrons bound in hydrogenlike ions. We discuss applications of these observations in the determination of fundamental physical constants, the fine structure constant, the electron mass, and in searches for new interactions.
2006
Article
http://edoc.mpg.de/284815
Canadian Journal of Physics, v.84, 1-10 (2006)
en
oai:edoc.mpg.de:2848162006-08-1737:954
Probing Proton Dynamics in Molecules on an Attosecond Time Scale
Baker, S.
Robinson, J. S.
Haworth, C. A.
Teng, H.
Smith, R. A.
Chirila, Ciprian C.
Lein, Manfred
Tisch, J. W. G.
Marangos, J. P.
expertsonly
We demonstrate a technique that uses high-order harmonic generation in molecules to probe nuclear dynamics and structural rearrangement on a subfemtosecond time scale. The chirped nature of the electron wavepacket produced by laser ionization in a strong field gives rise to a similar chirp in the photons emitted upon electron-ion recombination. Use of this chirp in the emitted light allows information about nuclear dynamics to be gained with 100-attosecond temporal resolution, from excitation by an 8-femtosecond pulse, in a single laser shot. Measurements on molecular hydrogen and deuterium agreed well with calculations of ultrafast nuclear dynamics in the H2+ molecule, confirming the validity of the method. We then measured harmonic spectra from CH4 and CD4 to demonstrate a few-femtosecond time scale for the onset of proton rearrangement in methane upon ionization.
© 2006 American Association for the Advancement of Science
2006
Article
http://edoc.mpg.de/284816
info:doi/10.1126/science.1123904
Science, v.312, 424-427 (2006)
en
oai:edoc.mpg.de:2848172006-08-1737:954
Two-electron ionization and stabilization beyond the dipole approximation
Staudt, Andreas
Keitel, Christoph Helmut
expertsonly
A two-dimensional model atom is employed to study the ionization behavior of helium subjected to strong laser fields in the high-frequency regime. The evolution of the system is studied by means of numerical integration of the Schrödinger equation beyond the dipole approximation. Ionization probabilities of the two-electron atom in highly intense laser fields have been calculated for different pulse shapes. It is confirmed that the mutual repulsion between the two electrons as well as the length of the laser pulses significantly alter the ionization probabilities of the system. Nondipole effects are shown to lead to a considerable increase of the ionization probabilities. For certain laser pulse shapes, a regime of ionization suppression is investigated which exists in addition to two-electron stabilization. The applicability of our model scheme to the case of heliumlike systems is discussed, and it is shown that stabilization may also occur in these systems, and how it is altered in dependence of the nuclear charge.
©2006 The American Physical Society
2006
Article
http://edoc.mpg.de/284817
info:doi/10.1103/PhysRevA.73.043412
Physical Review A, v.73 (2006)
en
oai:edoc.mpg.de:2848182006-08-1737:954
Relativistic high-power laser–matter interactions
Salamin, Yousef I.
Hu, S. X.
Hatsagortsyan, Karen Zaven
Keitel, Christoph Helmut
expertsonly
Recent advances in laser technology have pushed the frontier of maximum intensity achieved to about and investigators currently believe even higher intensities may be reached in the near future. This, combined with other breakthroughs on the fronts of short pulse generation and high repetition rates, have stimulated considerable progress, theoretical as well as experimental, in the field of laser–matter interactions. It is now possible to laser-accelerate electrons to a few hundred MeV and laser-induced pair-production and nuclear physics experiments have made significant progress. This article is devoted to a review of the recent advances in the field and stresses quantum phenomena that require laser field intensities in excess of the relativistic threshold of . Interactions with free electrons, with highly-charged ions and with atoms and clusters, are reviewed. Electron laser acceleration, atomic quantum dynamics, high harmonic generation, quantum electrodynamical effects and nuclear interactions in plasmas and ions, are among the important topics covered in the article.
© 2006 Elsevier B.V.
2006
Article
http://edoc.mpg.de/284818
info:doi/10.1016/j.physrep.2006.01.002
Physics Reports, v.427, 41-155 (2006)
en
oai:edoc.mpg.de:2852912006-08-1737:954
Nuclear Quantum Optics with X-Ray Laser Pulses
Bürvenich, Thomas J.
Evers, Jörg
Keitel, Christoph Helmut
expertsonly
The direct interaction of nuclei with superintense laser fields is studied. We show that present and upcoming high-frequency laser facilities, especially together with a moderate acceleration of the target nuclei to match photon and transition frequency, do allow for resonant laser-nucleus interaction. These direct interactions may be utilized for the model-independent optical measurement of nuclear properties such as the transition frequency and the dipole moment, thus opening the field of nuclear quantum optics. As an ultimate goal, one may hope that direct laser-nucleus interactions could become a versatile tool to enhance preparation, control, and detection in nuclear physics.
©2006 The American Physical Society
2006
Article
http://edoc.mpg.de/285291
info:doi/10.1103/PhysRevLett.96.142501
Physical Review Letters, v.96 (2006)
en
oai:edoc.mpg.de:2852922007-09-1937:954
Nonlinear Resonance Absorption in the Laser-Cluster Interaction
Kundu, Mrityunjay
Bauer, Dieter
expertsonly
Rare-gas or metal clusters are known to absorb laser energy very efficiently. Upon cluster expansion, the Mie plasma frequency may become equal to the laser frequency. This linear resonance has been well studied both experimentally and theoretically employing pump probe schemes. In this work, we focus on the few-cycle regime or the early stage of the cluster dynamics, where linear resonance is not met but, nevertheless, efficient absorption of laser energy persists. By retrieving time-dependent oscillator frequencies from particle-in-cell simulation results, we show that nonlinear resonance is the dominant mechanism behind outer ionization and energy absorption in near infrared laser-driven clusters.
©2006 The American Physical Society
2006
Article
http://edoc.mpg.de/285292
info:doi/10.1103/PhysRevLett.96.123401
Physical Review Letters, v.96, 1-4 (2006)
en
oai:edoc.mpg.de:2852932007-09-1937:954
QPROP: A Schrödinger-solver for intense laser–atom interaction
Bauer, Dieter
Koval, Peter
expertsonly
The Qprop package is presented. Qprop has been developed to study laser–atom interaction in the nonperturbative regime where nonlinear phenomena such as above-threshold ionization, high order harmonic generation, and dynamic stabilization are known to occur. In the nonrelativistic regime and within the single active electron approximation, these phenomena can be studied with Qprop in the most rigorous way by solving the time-dependent Schrödinger equation in three spatial dimensions. Because Qprop is optimized for the study of quantum systems that are spherically symmetric in their initial, unperturbed configuration, all wavefunctions are expanded in spherical harmonics. Time-propagation of the wavefunctions is performed using a split-operator approach. Photoelectron spectra are calculated employing a window-operator technique. Besides the solution of the time-dependent Schrödinger equation in single active electron approximation, Qprop allows to study many-electron systems via the solution of the time-dependent Kohn–Sham equations.
© 2005 Elsevier B.V.
2006
Article
http://edoc.mpg.de/285293
info:doi/10.1016/j.cpc.2005.11.001
Computer Physics Communications, v.174, 396-421 (2006)
en
oai:edoc.mpg.de:2852942008-03-0337:954
Radiative electron capture into high-Z few-electron ions: Alignment of the excited ionic states
Surzhykov, Andrey
Jentschura, Ulrich David
Stöhlker, Thomas
Fritzsche, Stephan
expertsonly
We lay out a unified formalism for the description of radiative electron capture into excited states of heavy, few-electron ions and their subsequent decay, including a full account of many-electron effects and higher-order multipoles of the radiation field. In particular, the density-matrix theory is applied to explore the magnetic sublevel population of the residual ions, as described in terms of alignment parameters. For the electron capture into the initially hydrogenlike U91+ and lithiumlike U89+ uranium projectiles, the alignment parameters are calculated, within the multiconfiguration Dirac-Fock approach, as a function of the collision energy and for different ionic states. From these calculations, we find that the many-electron interactions may result in a small enhancement of the alignment, and that this effect becomes more pronounced for highly excited levels.
©2006 The American Physical Society
2006
Article
http://edoc.mpg.de/285294
info:doi/10.1103/PhysRevA.73.032716
Physical Review A, v.73, 1-8 (2006)
en
oai:edoc.mpg.de:2856902006-08-1737:954
Strong-field approximation for harmonic generation in diatomic molecules
Chirila, Ciprian C.
Lein, Manfred
expertsonly
The generation of high-order harmonics in diatomic molecules is investigated within the framework of the strong-field approximation. We show that the conventional saddle-point approximation is not suitable for large internuclear distances. An adapted saddle-point method that takes into account the molecular structure is presented. We analyze the predictions for the harmonic-generation spectra in both the velocity and length gauges. At large internuclear separations, we compare the resulting cutoffs with the predictions of the three-step semiclassical mechanism. Good agreement is obtained only by using the adapted saddle-point method combined with the velocity gauge.
©2006 The American Physical Society
2006
Article
http://edoc.mpg.de/285690
info:doi/10.1103/PhysRevA.73.023410
Physical Review A, v.73 (2006)
en
oai:edoc.mpg.de:2856912006-08-1737:954
Geometry-dependent dynamics of two Λ-type atoms via vacuum-induced coherences
Evers, Jörg
Kiffner, Martin
Macovei, Mihai
Keitel, Christoph Helmut
expertsonly
The dynamics of a pair of atoms can significantly differ from the single-atom dynamics if the distance of the two atoms is small on a scale given by the relevant transition wavelengths. Here, we discuss two nearby three-level atoms in Λ configuration, and focus on the dependence of the optical properties on the geometry of the setup. We find that in general transitions in the two atoms can be dipole-dipole coupled by interactions via the vacuum field even if their transition dipole moments are orthogonal. We give an interpretation of this effect and show that it may crucially influence the system dynamics. In particular, for a fixed setup of driving fields and detectors, the spatial orientation of the two-atom pair decides if the system reaches a true constant steady state or if it exhibits periodic oscillations in the long-time limit. As an example observable, we study the resonance fluorescence intensity, which is either constant or is modulated periodically in the long-time limit.
©2006 The American Physical Society
2006
Article
http://edoc.mpg.de/285691
info:doi/10.1103/PhysRevA.73.023804
Physical Review A, v.73 (2006)
en
oai:edoc.mpg.de:2856942006-08-1737:954
Influence of nuclear vibration on harmonic generation in molecules
Chirila, Ciprian C.
Lein, Manfred
expertsonly
The effect of vibrational motion on harmonic generation in molecules is studied within the strong-field approximation. Simple expressions are given for the cut-off energy and for the ratio of spectral intensities from two isotopes. The latter is based on electronic trajectories from the simple-man's model. The influence of vibration is given by a correlation function that is sensitive to the overlap between the initial vibrational wave packet and the wave packet after the evolution in the Born–Oppenheimer potential of the ionized molecule.
© Institute of Physics and IOP Publishing Limited 2006
2006
Article
http://edoc.mpg.de/285694
info:doi/10.1088/0953-4075/39/13/S17
Journal of Physics B, v.39, 437-444 (2006)
en
oai:edoc.mpg.de:2857022006-08-1737:954
Ionization suppression of excited atomic states beyond the stabilization regime
Staudt, Andreas
Keitel, Christoph Helmut
Briggs, John S.
expertsonly
A two-dimensional model atom is employed to study the ionization behaviour of initially excited atomic states in intense high frequency laser pulses beyond the dipole approximation. An additional regime of ionization suppression is found at laser intensities where the stabilization effect is expected to break down. The appearance of this effect is due to a strong coupling of the initial wavefunction to the ground state of the cycle-averaged space-translated ionic potential, followed by a subsequent population transfer to the ground state during the laser pulse turn-off. Non-dipole effects are found to increase the overall ionization probabilities, but not to suppress or alter this effect substantially.
© Institute of Physics and IOP Publishing Limited 2006
2006
Article
http://edoc.mpg.de/285702
info:doi/10.1088/0953-4075/39/3/016
Journal of Physics B, v.39, 633-639 (2006)
en
oai:edoc.mpg.de:2857722006-08-2137:954
Irreversible energy gain by linear and nonlinear oscillators
Bauer, Dieter
Mulser, P.
notspecified
© Institute of Physics and IOP Publishing Limited 2006
2005
Conference-Paper
http://edoc.mpg.de/285772
info:doi/10.1088/1742-6596/11/1/017
Journal of Physics: Conference Series, v.11, 169-179 (2005)
en
oai:edoc.mpg.de:2857772006-08-2137:954
Vacuum-mediated incoherent processes in coherently prepared media
Evers, Jörg
Jentschura, Ulrich David
Macovei, Mihai
Keitel, Christoph Helmut
expertsonly
We discuss various aspects of the incoherent spontaneous emission in atomic few-level systems arising from the coupling of the atom to the surrounding vacuum. First, we consider systems where the decoherence due to spontaneous emission acts as a limiting factor. Here, we combine collective effects in larger samples of atoms with control mechanisms known from single-atom schemes, or modifiy the system dynamics by externally inducing multiphoton quantum interference effects. In the second part, we discuss ground-state laser cooling of trapped atoms and ions. Here, the momentum transfer in the spontaneous emission events is required to cool the particles, but needs to be controlled in order to achieve a low cooling limit. In our scheme, we make use of double electromagnetically induced transparency in order to design the absorption spectrum of the trapped particle. In the final part, we show that the incoherent part of the resonance fluorescence spectrum of a two-level system may serve as an interesting candidate for high-precision spectroscopy. For this, we discuss relativistic and radiative corrections to the resonance fluorescence spectra of laser-driven few-level systems.
SPIE
© 2005 The Society of Photo-Optical Engineering
2005
Conference-Paper
http://edoc.mpg.de/285777
info:doi/10.1117/12.609233
Hemmer, Philip R.: Fluctuations and noise in photonics and quantum optics III, SPIE (2005)
en
oai:edoc.mpg.de:2857962006-08-2137:954
Toward high-precision values of the self energy of non-S states in hydrogen and hydrogen-like ions
Le Bigot, E.-O.
Jentschura, Ulrich David
Indelicato, P.
Mohr, P. J.
expertsonly
The method and status of a study to provide numerical, high-precision values of the self-energy level shift in hydrogen and hydrogen-like ions is described. Graphs of the self energy in hydrogen-like ions with nuclear charge number between 20 and 110 are given for a large number of states. The self-energy is the largest contribution of quantum electrodynamics (QED) to the energy levels of these atomic systems. These results greatly expand the number of levels for which the self energy is known with a controlled and high precision. Applications include the adjustment of the Rydberg constant and atomic calculations that take into account QED effects.
© 2005 NRC Canada
2005
Article
http://edoc.mpg.de/285796
info:doi/10.1139/P04-076
Canadian Journal of Physics, v.83, 447-454 (2005)
en
oai:edoc.mpg.de:2857972006-08-2137:954
Nonrelativistic QED approach to the Lamb shift
Jentschura, Ulrich David
Czarnecki, Andrzej
Pachucki, Krzysztof
expertsonly
We calculate the one- and two-loop corrections of order (Z)6 and 2(Z)6, respectively, to the Lamb shift in hydrogenlike systems using the formalism of nonrelativistic quantum electrodynamics. We obtain general results valid for all hydrogenic states with nonvanishing orbital angular momentum and for the normalized difference of S states. These results involve the expectation value of local effective operators and relativistic corrections to Bethe logarithms. The one-loop correction is in agreement with previous calculations for the particular cases of S, P, and D states. The two-loop correction in the order 2(Z)6 includes the pure two-loop self-energy and all diagrams with closed fermion loops. The obtained results allow one to obtain improved theoretical predictions for all excited hydrogenic states.
©2005 The American Physical Society
2005
Article
http://edoc.mpg.de/285797
Physical Review A, v.72, 1-20 (2005)
en
oai:edoc.mpg.de:2857992007-03-1637:954
Nonperturbative multiphoton processes and electron-positron pair production
Hatsagortsyan, Karen Zaven
Müller, Carsten
Keitel, Christoph Helmut
expertsonly
Various regimes of pair production in laser fields are analyzed. Particularly, the question of the observability of pair production in a nonperturbative multiphoton regime is discussed. A simple heuristic method is employed which gives order-of-magnitude estimates for probabilities of multiphoton processes and allows to describe its main features. The method is initially probed upon the known process of pair production in a Coulomb and a strong laser field. Then it is applied to the nonperturbative multiphoton regime of the pair production process in a standing laser wave.
AIP
©2006 American Institute of Physics
2006
Conference-Paper
http://edoc.mpg.de/285799
info:doi/10.1063/1.2195234
Batani, Dimitri ; Lontano, Maurizio: Superstrong fields in plasmas : Third International Conference on Superstrong Fields in Plasmas, Varenna, Italy, 19 - 24 September 2005 ; [selected papers], AIP, 442-447 (2006)
en
oai:edoc.mpg.de:2858002007-03-1637:954
Harmonic generation from laser-driven vacuum
Di Piazza, Antonino
Hatsagortsyan, Karen Zaven
Keitel, Christoph Helmut
expertsonly
We investigate harmonic generation from vacuum in the field of a superstrong standing laser wave. We show analitycally that for laser electric fields larger than Ecr = m2c3/e = 1.3 · 1016 V/cm high order harmonics of the pumping laser are generated. The harmonic spectrum shows a wide plateau followed by a cut-off at photon energies M ~ with EL the amplitude of the 6laser field. In the weak field limit EL Ecr the emission of high harmonics is very unlikely. This is now the experimentally interesting case and we show that "laser assisted" photon-photon scattering could be observed with optical lasers available today.
AIP
© 2006 American Institute of Physics
2006
Conference-Paper
http://edoc.mpg.de/285800
info:doi/10.1063/1.2195233
Batani, Dimitri ; Lontano, Maurizio: Superstrong fields in plasmas : Third International Conference on Superstrong Fields in Plasmas, Varenna, Italy, 19 - 24 September 2005 ; [selected papers], AIP, 436-441 (2006)
en
oai:edoc.mpg.de:2858012006-08-2137:954
QED Corrections to the Dynamic Polarizability
Haas, Martin
Jentschura, Ulrich David
Keitel, Christoph Helmut
expertsonly
In a relatively weak laser field, atoms interacting with one-photon off-resonant laser fields are dynamically polarized. This perturbation manifests itself in a shift of the atomic energy levels called the "dynamic Stark effect" or "AC-Stark effect", which is intensity dependent. The AC-Stark coefficients are therefore of particular importance for high-precision spectroscopy experiments which rely on two-photon processes like the 1S-2S transition in hydrogen, hydrogenlike ions, antihydrogen or similar composite matter-antimatter systems. In addition, the imaginary part of the dynamic polarizability determines the resonant one-photon ionization width for the excited level.Up to now, the dynamic polarizability has been investigated only up to the level of relativistic corrections. In this contribution, we present results for several experimentally relevant transitions in hydrogenlike systems and the leading-order QED radiative corrections.
AIP
©2005 American Institute of Physics
2005
Conference-Paper
http://edoc.mpg.de/285801
info:doi/10.1063/1.2130187
Grzonka, Dieter: Low energy antiproton physics : Eighth International Conference on Low Energy Antiproton Physics (LEAP '05) Bonn, Germany 13 - 22 May 2005, AIP (2005)
en
oai:edoc.mpg.de:2879662006-10-0537:954
Controlling multiparticle correlations with a strong laser field
Dal Col, Mario
Macovei, Mihai
Keitel, Christoph Helmut
expertsonly
The collective interaction via a surrounding thermalized electromagnetic reservoir of a two-level multiatom sample with an external applied strong coherent field is investigated. In a small sample following Dicke’s model, even at the exact resonances, very strong pumping leads to a complete transfer of the population into a particular dressed-state. This way very large Rabi frequencies are shown to modify and control the interatomic correlations in a system of spatially separated atoms of few wavelengths extend.
© 2006 Elsevier B.V.
2006
Article
http://edoc.mpg.de/287966
info:doi/10.1016/j.optcom.2006.02.062
Optics Communications, v.264, 407-412 (2006)
en
oai:edoc.mpg.de:2879672006-10-0537:954
Microscopic laser-driven high-energy colliders
Hatsagortsyan, Karen Zaven
Müller, Carsten
Keitel, Christoph Helmut
expertsonly
The concept of a laser-guided e+e- collider in the single-femtosecond and high-energy regime is presented and its feasibility discussed. Ultra-intense laser pulses and strong static magnetic fields are employed to unite in one stage the electron and positron acceleration and their microscopic coherent collision in the GeV regime. We show that such coherent collisions yield a very large enhancement of the luminosity as compared to conventional incoherent colliders.
© EDP Sciences 2006
2006
Article
http://edoc.mpg.de/287967
info:doi/10.1209/epl/i2006-10226-2
Europhysics Letters, v.76, 29-35 (2006)
en
oai:edoc.mpg.de:2879682006-10-0537:954
Light Diffraction by a Strong Standing Electromagnetic Wave
Di Piazza, Antonino
Hatsagortsyan, Karen Zaven
Keitel, Christoph Helmut
expertsonly
The nonlinear quantum interaction of a linearly polarized x-ray probe beam with a focused intense standing laser wave is studied theoretically. Because of the tight focusing of the standing laser pulse, diffraction effects arise for the probe beam as opposed to the corresponding plane wave scenario. A quantitative estimate for realistic experimental conditions of the ellipticity and the rotation of the main polarization plane acquired by the x-ray probe after the interaction shows that the implementation of such vacuum effects is feasible with future X-ray Free Electron Laser light.
©2006 The American Physical Society
2006
Article
http://edoc.mpg.de/287968
info:doi/10.1103/PhysRevLett.97.083603
Physical Review Letters, v.97, 1-4 (2006)
en
oai:edoc.mpg.de:2879692008-03-0337:954
Exploring Relativistic Many-Body Recoil Effects in Highly Charged Ions
Soria Orts, Rosario
Harman, Zoltan
Crespo López-Urrutia, José R.
Artemyev, Anton N.
Bruhns, Hjalmar
González Martínez, Antonio J.
Jentschura, Ulrich David
Keitel, Christoph Helmut
Lapierre, Alain
Mironov, V.
Shabaev, V. M.
Tawara, Hiroyuki
Tupitsyn, Ilya I.
Ullrich, Joachim
Volotka, A. V.
expertsonly
The relativistic recoil effect has been the object of experimental investigations using highly charged ions at the Heidelberg electron beam ion trap. Its scaling with the nuclear charge Z boosts its contribution to a measurable level in the magnetic-dipole (M1) transitions of B- and Be-like Ar ions. The isotope shifts of 36Ar versus 40Ar have been detected with sub-ppm accuracy, and the recoil effect contribution was extracted from the 1s22s22p 2P1/2-2P3/2 transition in Ar13+ and the 1s22s2p 3P1-3P2 transition in Ar14+. The experimental isotope shifts of 0.00123(6) nm (Ar13+) and 0.00120(10) nm (Ar14+) are in agreement with our present predictions of 0.00123(5) nm (Ar13+) and 0.00122(5) nm (Ar14+) based on the total relativistic recoil operator, confirming that a thorough understanding of correlated relativistic electron dynamics is necessary even in a region of intermediate nuclear charges.
©2006 The American Physical Society
2006
Article
http://edoc.mpg.de/287969
info:doi/10.1103/PhysRevLett.97.103002
Physical Review Letters, v.97, 1-4 (2006)
en
oai:edoc.mpg.de:2879702006-10-0537:954
Enhanced Recollisions for Antisymmetric Molecular Orbitals in Intense Laser Fields
Fischer, Robert
Lein, Manfred
Keitel, Christoph Helmut
expertsonly
The peculiarities of antisymmetric molecular orbitals are investigated in very intense linearly polarized laser pulses. For this purpose, the ionization-recollision quantum dynamics is evaluated theoretically beyond the dipole approximation. As opposed to the usual situation, the laser magnetic field component is found to strongly enhance recollision probabilities for particularly oriented antisymmetric molecular orbitals. Harmonic generation and related processes are thus allowed at high laser intensities without the common limitations by the laser magnetic field.
©2006 The American Physical Society
2006
Article
http://edoc.mpg.de/287970
info:doi/10.1103/PhysRevLett.97.143901
Physical Review Letters, v.97, 1-4 (2006)
en
oai:edoc.mpg.de:2879712006-10-0537:954
Dynamic nuclear Stark shift in superintense laser fields
Bürvenich, Thomas J.
Evers, Jörg
Keitel, Christoph Helmut
expertsonly
The direct interaction of superintense laser fields in the optical frequency domain with nuclei is studied. As main observable, we consider the nuclear dynamic (AC) Stark shift of low-lying nuclear states due to the off-resonant excitation by the laser field. We include the case of accelerated nuclei to be able to control the frequency and the intensity of the laser field in the nuclear rest frame over a wide range of parameters. We find that AC-Stark shifts of the same order as in typical quantum optical systems relative to the respective transition frequencies are feasible with state-of-the-art or near-future laser field intensities and moderate acceleration of the target nuclei. Along with this shift, but only at intensities above the critical field strength, we find laser-induced modifications to the proton root-mean-square radii and to the proton density distribution. We thus expect direct laser-nucleus interaction to become of relevance together with other super-intense light-matter interaction processes such as pair creation.
©2006 The American Physical Society
2006
Article
http://edoc.mpg.de/287971
info:doi/10.1103/PhysRevC.74.044601
Physical Review C, v.74, 1-9 (2006)
en
oai:edoc.mpg.de:2994362007-02-2637:954
Muon pair creation from positronium in a circularly polarized laser field
Müller, Carsten
Hatsagortsyan, Karen Zaven
Keitel, Christoph Helmut
expertsonly
We study elementary particle reactions that result from the interaction of an atomic system with a very intense laser wave of circular polarization. As a specific example, we calculate the rate for the laser-driven reaction e+e--->µ+µ-, where the electron and positron originate from a positronium atom or, alternatively, from a nonrelativistic e+e- plasma. We distinguish accordingly between the coherent and incoherent channels of the process. Apart from numerical calculations, we derive by analytical means compact formulas for the corresponding reaction rates. The rate for the coherent channel in a laser field of circular polarization is shown to be damped because of the destructive interference of the partial waves that constitute the positronium ground-state wave packet. Conditions for the observation of the process via the dominant incoherent channel in a circularly polarized field are pointed out.
©2006 The American Physical Society
2006
Article
http://edoc.mpg.de/299436
info:doi/10.1103/PhysRevD.74.074017
Physical Review D, v.74, 1-16 (2006)
en
oai:edoc.mpg.de:2994442007-02-2637:954
Distilling two-atom distance information from intensity-intensity correlation functions
Chang, Jun-Tao
Evers, Jörg
Zubairy, M. Suhail
expertsonly
The intensity-intensity correlation function of the resonance fluorescence light of two two-level atoms driven by a resonant standing-wave laser field is examined. Our aim is to gain information on the distance between the two atoms from observables accessible in experiments. For this, we numerically solve the time-evolution equations of the system and calculate the steady-state intensity-intensity correlation by using the Laplace transform and quantum regression theory. By varying the interatomic distance from about half a wavelength down to small fractions of a wavelength, we show that the correlation function exhibits characteristic properties for different distance ranges. Based on these results, we propose a scheme to obtain interatomic distance information from the power spectrum of the correlation function, which allows us to extract the desired distance information over a wide range of distances with high accuracy.
©2006 The American Physical Society
2006
Article
http://edoc.mpg.de/299444
info:doi/10.1103/PhysRevA.74.043820
Physical Review A, v.74, 1-9 (2006)
en
oai:edoc.mpg.de:2994482008-03-0337:954
Effective action and phase structure of multi-layer sine-Gordon type models
Jentschura, Ulrich David
Nándori, István
Zinn-Justin, Jean
expertsonly
We analyze the effective action and the phase structure of Ν-layer sine-Gordon type models, generalizing the results obtained for the two-layer sine-Gordon model found in [I. Nándori, S. Nagy, K. Sailer, U.D. Jentschura, Nucl. Phys. B, 725 (2005) 467–492]. Besides the obvious field theoretical interest, the layered sine-Gordon model has been used to describe the vortex properties of high transition temperature superconductors, and the extension of the previous analysis to a general N-layer model is necessary for a description of the critical behaviour of vortices in realistic multi-layer systems. The distinction of the Lagrangians in terms of mass eigenvalues is found to be the decisive parameter with respect to the phase structure of the N-layer models, with neighboring layers being coupled by quadratic terms in the field variables. By a suitable rotation of the field variables, we identify the periodic modes (without explicit mass terms) in the N-layer structure, calculate the effective action and determine their Kosterlitz–Thouless type phase transitions to occur at a coupling parameter β2c,N=8Nπ, where N is the number of layers (or flavors in terms of the multi-flavor Schwinger model).
© 2006 Elsevier Inc.
2006
Article
http://edoc.mpg.de/299448
info:doi/10.1016/j.aop.2006.01.005
Annals of Physics, v.321, 2647-2659 (2006)
en
oai:edoc.mpg.de:2994522008-03-0337:954
Quantum dot potentials: Symanzik scaling, resurgent expansions, and quantum dynamics
Surzhykov, Andrey
Lubasch, Michael
Zinn-Justin, Jean
Jentschura, Ulrich David
expertsonly
This article is concerned with a special class of the "double-well-like" potentials that occur naturally in the analysis of finite quantum systems. Special attention is paid, in particular, to the so-called Fokker-Planck potential, which has a particular property: the perturbation series for the ground-state energy vanishes to all orders in the coupling parameter, but the actual ground-state energy is positive and dominated by instanton configurations of the form exp(−a/g), where a is the instanton action. The instanton effects are most naturally taken into account within the modified Bohr-Sommerfeld quantization conditions whose expansion leads to the generalized perturbative expansions (so-called resurgent expansions) for the energy eigenvalues of the Fokker-Planck potential. Until now, these resurgent expansions have been mainly applied for small values of coupling parameter g, while much less attention has been paid to the strong-coupling regime. In this contribution, we compare the energy values, obtained by directly resumming generalized Bohr-Sommerfeld quantization conditions, to the strong-coupling expansion, for which we determine the first few expansion coefficients in powers of g−2/3. Detailed calculations are performed for a wide range of coupling parameters g and indicate a considerable overlap between the regions of validity of the weak-coupling resurgent series and of the strong-coupling expansion. Apart from the analysis of the energy spectrum of the Fokker-Planck Hamiltonian, we also briefly discuss the computation of its eigenfunctions. These eigenfunctions may be utilized for the numerical integration of the (single-particle) time-dependent Schrödinger equation and, hence, for studying the dynamical evolution of the wave packets in the double-well-like potentials.
©2006 The American Physical Society
2006
Article
http://edoc.mpg.de/299452
info:doi/10.1103/PhysRevB.74.205317
Physical Review B, v.74, 1-13 (2006)
en
oai:edoc.mpg.de:2994562007-02-2637:954
High-order above-threshold ionization in stretched molecules
Chirila, Ciprian C.
Lein, Manfred
expertsonly
By numerical solution of the time-dependent Schrödinger equation, highly accurate electron spectra are calculated for strong-field ionization of a one-dimensional H2+ molecular ion at large internuclear distances. Compared to the atomic spectra, we find additional cutoffs at high electron energies. The classical model for ionization (simple-man's model) adapted to the molecular geometry predicts cutoffs up to 50Up, where Up is the ponderomotive potential. The cutoffs correspond to various scattering scenarios of the tunneled electron from the molecular sites. For certain internuclear distances the agreement between the classical predictions and the numerical spectra is unsatisfactory. We propose a modified simple-man's model based on complex electron trajectories, allowing for electrons appearing in the continuum with nonzero initial velocity from the tunneling ionization process. Agreement of the resulting cutoffs with the numerical results is recovered.
©2006 The American Physical Society
2006
Article
http://edoc.mpg.de/299456
info:doi/10.1103/PhysRevA.74.051401
Physical Review A, v.74, 1-4 (2006)
en
oai:edoc.mpg.de:2994842010-05-2537:954
Photoionization broadening of the 1S-2S transition in a beam of atomic hydrogen
Kolachevsky, Nikolai
Haas, Martin
Jentschura, Ulrich David
Herrmann, Maximilian
Fendel, Peter
Fischer, Marc
Holzwarth, Ronald
Udem, Thomas
Keitel, Christoph Helmut
Hänsch, Theodor W.
expertsonly
We consider the excitation dynamics of the two-photon 1S-2S transition in a beam of atomic hydrogen by 243 nm laser radiation. Specifically, we study the impact of ionization damping on the transition line shape, caused by the possibility of ionization of the 2S level by the same laser field. Using a Monte Carlo simulation, we calculate the line shape of the 1S-2S transition for the experimental geometry used in the two latest absolute frequency measurements [M. Niering et al., Phys. Rev. Lett. 84, 5496 (2000) and M. Fischer et al., Phys. Rev. Lett. 92, 230802 (2004)]. The calculated line shift and linewidth are in excellent agreement with the experimentally observed values. From this comparison we can verify the values of the dynamic Stark shift coefficient for the 1S-2S transition for the first time on a level of 15%. We show that the ionization modifies the velocity distribution of the metastable atoms, the line shape of the 1S-2S transition, and has an influence on the derivation of its absolute frequency.
©2006 The American Physical Society
2006
Article
http://edoc.mpg.de/299484
info:doi/10.1103/PhysRevA.74.052504
Physical Review A, v.74, 1-9 (2006)
en
oai:edoc.mpg.de:2994942008-03-0337:954
Kα1 radiation from heavy, heliumlike ions produced in relativistic collisions
Surzhykov, Andrey
Jentschura, Ulrich David
Stöhlker, Thomas
Fritzsche, Stephan
expertsonly
Bound-state transitions in few-electron, heavy ions following radiative electron capture are studied within the framework of the density matrix theory and the multiconfiguration Dirac-Fock approach. Special attention is paid to the Kα1 (1s1/22p3/2 1,3PJ=1,2-->1s1/22 1SJ=0) radiative decay of heliumlike uranium U90+ projectiles. This decay has recently been observed at the GSI facility in Darmstadt, giving rise to a surprisingly isotropic angular distribution, which is inconsistent with previous experiments and calculations based on a "one-particle" model. We show that the unexpected isotropy essentially results from the mutual cancellation of the angular distributions of the 1P1-->¹S₀ electric dipole and ³P₂-->¹S₀ magnetic quadrupole transitions, both of which contribute to the Kα₁ radiation. Detailed computations on the anisotropy of the Kα₁ radiation have been carried out for a wide range of projectile energies and are compared to available experimental data.
©2006 The American Physical Society
2006
Article
http://edoc.mpg.de/299494
info:doi/10.1103/PhysRevA.74.052710
Physical Review A, v.74, 1-5 (2006)
en
oai:edoc.mpg.de:2995012007-09-2037:954
Adiabatic Approximation of the Correlation Function in the Density-Functional Treatment of Ionization Processes
Wilken, Florian
Bauer, Dieter
expertsonly
The ionization of a one-dimensional model helium atom in short laser pulses using time-dependent density-functional theory is investigated. We calculate ionization probabilities as a function of laser intensity by approximating the correlation function of the system adiabatically with an explicit dependence on the fractional number of bound electrons. For the correlation potential we take the derivative discontinuity at integer numbers of bound electrons explicitly into account. This approach reproduces ionization probabilities from the solution of the time-dependent Schrödinger equation, in particular, the so-called knee due to nonsequential ionization.
©2006 The American Physical Society
2006
Article
http://edoc.mpg.de/299501
info:doi/10.1103/PhysRevLett.97.203001
Physical Review Letters, v.97, 1-4 (2006)
en
oai:edoc.mpg.de:2995102007-02-2637:954
Relativistic ionization rescattering with tailored laser pulses
Klaiber, Michael
Hatsagortsyan, Karen Zaven
Keitel, Christoph Helmut
expertsonly
The interaction of relativistically strong tailored laser pulses with an atomic system is considered. Due to special tailoring of the laser pulse, the suppression of the relativistic drift of the ionized electron and a dramatic enhancement of the rescattering probability is shown to be achievable. The high harmonic generation rate in the relativistic regime is calculated and shown to be increased by several orders of magnitude compared to the case of conventional laser pulses. The energies of the revisiting electron at the atomic core can approach the MeV domain, thus rendering hard x-ray harmonics and nuclear reactions with single atoms feasible.
©2006 The American Physical Society
2006
Article
http://edoc.mpg.de/299510
info:doi/10.1103/PhysRevA.74.051803
Physical Review A, v.74, 1-4 (2006)
en
oai:edoc.mpg.de:2995112007-09-1837:954
Collisionless energy absorption in the short-pulse intense laser-cluster interaction
Kundu, Mrityunjay
Bauer, Dieter
expertsonly
In a previous paper [Phys. Rev. Lett. 96, 123401 (2006)] we have shown by means of three-dimensional particle-in-cell simulations and a simple rigid-sphere model that nonlinear resonance absorption is the dominant collisionless absorption mechanism in the intense, short-pulse laser cluster interaction. In this paper we present a more detailed account of the matter. In particular we show that the absorption efficiency is almost independent of the laser polarization. In the rigid-sphere model, the absorbed energy increases by many orders of magnitude at a certain threshold laser intensity. The particle-in-cell results display maximum fractional absorption around the same intensity. We calculate the threshold intensity and show that it is underestimated by the common overbarrier ionization estimate.
©2006 The American Physical Society
2006
Article
http://edoc.mpg.de/299511
info:doi/10.1103/PhysRevA.74.063202
Physical Review A, v.74, 1-11 (2006)
en
oai:edoc.mpg.de:2995192007-02-2637:954
Light propagation through closed-loop atomic media beyond the multiphoton resonance condition
Mahmoudi, Mohammad
Evers, Jörg
expertsonly
The light propagation of a probe field pulse in a four-level double-lambda type system driven by laser fields that form a closed interaction loop is studied. The finite frequency width of the probe pulse requires a time-dependent analysis beyond the multiphoton resonance assumption. We apply a Floquet decomposition to the equations of motion to solve this time-dependent problem and to identify the different scattering processes contributing to the medium response. We find that the response oscillating in phase with the probe field is phase-independent. The phase dependence arises from a scattering of the coupling fields into the probe field mode at a frequency which in general differs from the probe field frequency. In particular for short pulses with a large frequency width, inducing a closed loop interaction contour may lead to a distortion of the pulse shape via this phase-sensitive scattering. Finally, we demonstrate that both the closed loop and the nonclosed loop configuration allow for sub- and superluminal light propagation with small absorption or even gain, where one of the coupling field Rabi frequencies acts as a control parameter that enables one to switch between sub- and superluminal light propagation.
©2006 The American Physical Society
2006
Article
http://edoc.mpg.de/299519
info:doi/10.1103/PhysRevA.74.063827
Physical Review A, v.74, 1-10 (2006)
en
oai:edoc.mpg.de:2995242008-03-0337:954
Two-loop Bethe logarithms for non-S levels
Jentschura, Ulrich David
expertsonly
Two-loop Bethe logarithms are calculated for excited P and D states in hydrogenlike systems, and estimates are presented for all states with higher angular momenta. These results complete our knowledge of the P and D energy levels in hydrogen at the order of α⁸mec₂, where me is the electron mass and c is the speed of light, and scale as Z⁶, where Z is the nuclear charge number. Our analytic and numerical calculations are consistent with the complete absence of logarithmic terms of order (α/π)²(Zα)⁶ ln[(Zα)−2]mec² for D states and all states with higher angular momenta. For higher excited P and D states, a number of poles from lower-lying levels have to subtracted in the numerical evaluation. We find that, surprisingly, the corrections of the “squared decay-rate type” are the numerically dominant contributions in the order (α/π)²(Zα)⁶mec² for states with large angular momenta, and provide an estimate of the entire B₆₀ coefficient for Rydberg states with high angular momentum quantum numbers. Our results reach the predictive limits of the quantum electrodynamic theory of the Lamb shift.
©2006 The American Physical Society
2006
Article
http://edoc.mpg.de/299524
info:doi/10.1103/PhysRevA.74.062517
Physical Review A, v.74, 1-13 (2006)
en
oai:edoc.mpg.de:3357122008-03-0137:954
Model calculations of photoemission from a surface-deposited fullerene monolayer
Kidun, O.
Bauer, D.
Fominykh, N.
Berakdar, J.
expertsonly
2007
Article
http://edoc.mpg.de/335712
urn:ISSN:0953-4075
Journal of Physics B-Atomic Molecular and Optical Physics, v.40, 4617-4624 (2007)
en
oai:edoc.mpg.de:3358652008-03-0337:954
Applicability of layered sine-Gordon models to layered superconductors: II. The case of magnetic coupling
Nandori, I.
Vad, K.
Meszaros, S.
Jentschura, U. D.
Nagy, S.
Sailer, K.
expertsonly
2007
Article
http://edoc.mpg.de/335865
urn:ISSN:0953-8984
Journal of Physics-Condensed Matter, v.19 (2007)
en
oai:edoc.mpg.de:3359712008-03-0137:954
Nonperturbative resonant strong field ionization of atomic hydrogen
Girju, M. G.
Hristov, K.
Kidun, O.
Bauer, D.
expertsonly
2007
Article
http://edoc.mpg.de/335971
urn:ISSN:0953-4075
Journal of Physics B-Atomic Molecular and Optical Physics, v.40, 4165-4178 (2007)
en
oai:edoc.mpg.de:3359732008-03-0137:954
Enhancement of entanglement for two-mode fields generated from four-wave mixing with the help of the auxiliary atomic transition
Li, G. X.
Tan, H. T.
Macovei, M.
expertsonly
2007
Article
http://edoc.mpg.de/335973
urn:ISSN:1050-2947
Physical Review A, v.76 (2007)
en
oai:edoc.mpg.de:3359752010-09-2937:954
Zeeman splitting and g factor of the 1s22s22p 2P3/2 and 2P1/2 levels in Ar13+
Soria Orts, R.
Crespo López-Urrutia, J. R.
Bruhns, H.
Martinez, A. J. G.
Harman, Z.
Jentschura, U. D.
Keitel, C. H.
Lapierre, A.
Tawara, H.
Tupitsyn, I. I.
Ullrich, J.
Volotka, A. V.
expertsonly
2007
Article
http://edoc.mpg.de/335975
urn:ISSN:1050-2947
Physical Review A, v.76 (2007)
en
oai:edoc.mpg.de:3359812008-03-0137:954
Isomer triggering via nuclear excitation by electron capture
Palffy, A.
Evers, J.
Keitel, C. H.
expertsonly
2007
Article
http://edoc.mpg.de/335981
urn:ISSN:0031-9007
Physical Review Letters, v.99 (2007)
en
oai:edoc.mpg.de:3359842008-03-0137:954
Reconstruction of an arbitrarily polarized few-cycle laser pulse by two-dimensional streaking
Shvetsov-Shilovski, N. I.
Goreslavski, S. P.
Popruzhenko, S. V.
Becker, W.
Paulus, G. G.
expertsonly
2007
Article
http://edoc.mpg.de/335984
urn:ISSN:1612-2011
Laser Physics Letters, v.4, 726-733 (2007)
en
oai:edoc.mpg.de:3359872008-03-0137:954
Harmonic generation from laser-irradiated clusters
Kundu, M.
Popruzhenko, S. V.
Bauer, D.
expertsonly
2007
Article
http://edoc.mpg.de/335987
urn:ISSN:1050-2947
Physical Review A, v.76 (2007)
en
oai:edoc.mpg.de:3359882008-03-0137:954
Photon splitting in a laser field
Di Piazza, A.
Milstein, A. I.
Keitel, C. H.
expertsonly
2007
Article
http://edoc.mpg.de/335988
urn:ISSN:1050-2947
Physical Review A, v.76 (2007)
en
ResultSet_33XYlCGApLB_range_100-199