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          Institute: MPI für Kernphysik     Collection: Precision Spectroscopy and Ultracold Ensembles     Display Documents

ID: 441475.0, MPI für Kernphysik / Precision Spectroscopy and Ultracold Ensembles
Experimental Investigations of Ion Charge Distributions, Effective Electron Densities, and Electron-Ion Cloud Overlap in Electron Beam Ion Trap Plasma Using Extreme-Ultraviolet Spectroscopy
Authors:Liang, G. Y.; Crespo López-Urrutia, J. R.; Baumann, T. M.; Epp, S. W.; Gonchar, A.; Lapierre, A.; Mokler, P. H.; Simon, M. C.; Tawara, H.; Mäckel, V.; Yao, K.; Zhao, G.; Zou, Y.; Ullrich, J.
Date of Publication (YYYY-MM-DD):2009-08-17
Title of Journal:Astrophysical Journal
Journal Abbrev.:ApJ
Issue / Number:2
Start Page:838
End Page:850
Copyright:© Institute of Physics and IOP Publishing Limited 2009
Review Status:Peer-review
Audience:Experts Only
Abstract / Description:Spectra in the extreme ultraviolet range from 107 to 353 Å emitted from Fe ions in various ionization stages have been observed at the Heidelberg electron beam ion trap (EBIT) with a flat-field grating spectrometer. A series of transition lines and their intensities have been analyzed and compared with collisional-radiative simulations. The present collisional-radiative model reproduces well the relative line intensities and facilitates line identification of ions produced in the EBIT. The polarization effect on the line intensities resulting from nonthermal unidirectional electron impact was explored and found to be significant (up to 24%) for a few transition lines. Based upon the observed line intensities, relative charge state distributions (CSD) of ions were determined, which peaked at Fe23+ tailing toward lower charge states. Another simulation on ion charge distributions including the ionization and electron capture processes generated CSDs which are in general agreement with the measurements. By observing intensity ratios of specific lines from levels collisionally populated directly from the ground state and those starting from the metastable levels of Fe XXI, Fe X and other ionic states, the effective electron densities were extracted and found to depend on the ionic charge. Furthermore, it was found that the overlap of the ion cloud with the electron beam estimated from the effective electron densities strongly depends on the charge state of the ion considered, i.e. under the same EBIT conditions, higher charge ions show less expansion in the radial direction.
Free Keywords:line: identification; methods: analytical; methods: laboratory
External Publication Status:published
Document Type:Article
Communicated by:vogt
Affiliations:MPI für Kernphysik/Group of J. Ullrich/Electron Beam Ion Trap ( J.R. Crespo Lopez-Urrutia)
External Affiliations:National Astronomical Observatories, CAS, A20 Datun Road, Chaoyang District, Beijing 100012, China
TRIUMF, Canadian National Laboratory for Particle and Nuclear Physics, 4004 Wesbrook Mall, Vancouver, BC V6T 2A3, Canada
EBIT Lab, Modern Physics Institute, Fudan University, Shanghai 200433, People's Republic of China
Department of Physics, University of Strathclyde, Glasgow G4 0NG, UK
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