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          Institute: MPI für medizinische Forschung     Collection: Forschungsgruppe Prof. Dr. Haeberlen     Display Documents

ID: 23000.0, MPI für medizinische Forschung / Forschungsgruppe Prof. Dr. Haeberlen
Precision Measurement of the Quadrupole Coupling and Chemical Shift Tensors of the Deuterons in α-Calcium Formate
Translation of Title:Precision Measurement of the Quadrupole Coupling and Chemical Shift Tensors of the Deuterons in α-Calcium Formate
Authors:Schmitt, Heike; Zimmermann, Herbert; Körner, O.; Stumber, Michael; Meinel, Christoph; Haeberlen, Ulrich
Date of Publication (YYYY-MM-DD):2001-07
Title of Journal:Journal of Magnetic Resonance
Journal Abbrev.:J. Magn. Reson.
Issue / Number:1
Start Page:65
End Page:77
Review Status:Peer-review
Audience:Experts Only
Intended Educational Use:No
Abstract / Description:Using calcium formate, α-Ca(DCOO)2, as a test sample, we explore how precisely deuteron quadrupole coupling (QC) and chemical shift (CS) tensors Q and can currently be measured. The error limits, ±0.09 kHz for the components of Q and ±0.06 ppm for those of , are at least three times lower than in any comparable previous experiment. The concept of a new receiver is described. A signal/noise ratio of 100 is realized in single-shot FT spectra. The measurement strategies and a detailed error analysis are presented. The precision of the measurement of Q is limited by the uncertainty of the rotation angles of the sample and that of by the uncertainty of the phase correction parameters needed in FT spectroscopy. With a 4-sigma confidence, it is demonstrated for the first time that the unique QC tensor direction of a deuteron attached to a carbon deviates from the bond direction; the deviation found is (1.2±0.3°). Evidence is provided for intermolecular QC contributions. In terms of Q, their size is roughly 4 kHz. The deuteron QC tensors in -Ca(DCOO)2 (two independent deuteron sites) are remarkable in three respects. For deuterons attached to sp2 carbons, first, the asymmetry factors and, second, the quadrupole coupling constants CQ, are unusually small, 1=0.018, 2=0.011, and CQ1=(151.27±0.06) kHz, CQ2=(154.09±0.06) kHz. Third, the principal direction associated with the largest negative QC tensor component lies in and not, as usual, perpendicular to the molecular plane. A rationalization is provided for these observations. The CS tensors obtained are in quantitative agreement with the results of an earlier, less precise, line-narrowing multiple-pulse study of -Ca(HCOO)2. The assignment proposed in that work is confirmed. Finally we argue that a further 10-fold increase of the measurement precision of deuteron QC tensors, and a 2-fold increase of that of CS tensors, should be possible. We indicate the measures that need to be taken.
Free Keywords:precision deuteron quadrupole coupling; chemical shift tensors; relation to n-structure
External Publication Status:published
Document Type:Article
Communicated by:Wulf Kaiser
Affiliations:MPI für medizinische Forschung/Abteilung Biophysik/
MPI für medizinische Forschung/Abteilung Molekulare Neurobiologie/
MPI für medizinische Forschung/Forschungsgruppe Molekülkristalle/
Identifiers:URI:http://www.sciencedirect.com/science?_ob=ArticleUR... [Abstract]
URI:http://www.sciencedirect.com/science?_ob=MImg&_ima... [Fulltext PDF]
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