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Fingerprints of Damped Quantum Rotation Observed in Solid‐State Proton NMR Spectra
Author(s) -
Gutsche Peter,
Schmitt Heike,
Haeberlen Ulrich,
Ratajczyk Tomasz,
Szymanski Slawomir
Publication year - 2006
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.200500572
Subject(s) - spectral line , chemistry , coherence (philosophical gambling strategy) , proton , nmr spectra database , quantum tunnelling , rotation (mathematics) , molecular physics , nuclear magnetic resonance , quantum mechanics , physics , geometry , mathematics
10.1002/cphc.200500572.abs 1 H NMR spectra of the methyl group in an oriented crystal sample of methylmalonic acid with all three non‐methyl protons replaced by deuterons are interpreted in terms of the damped quantum rotation (DQR) theory of NMR line shapes. The DQR approach offers a perfect theoretical reproduction of the observed spectra while the conventional Alexander‐Binsch line‐shape model shows evident defects in the present case. The temperature trends of the quantities characterizing the coherent and incoherent dynamics of the methyl group in the DQR approach (the effective tunnelling frequency and two coherence‐damping rates) derived from the spectra are fairly reproduced using a model reported previously. The present findings provide further evidence of limitations to the validity of the common belief that molecular rate processes in condensed phases are necessarily classical.