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Figure 4
(a) and (b) Raman spectra of hydrogenated D-Ala (C3H7NO2) in the A-irreducible representation of the factor group D2 for several temperatures between 20 and 300 K in the region from 180 to 600 cm−1. A temperature-dependent band at 468 cm−1 appears below 200 K and is marked by (*). (c) Raman spectra in the A-irreducible y(zz)y representation of the factor group D2 for selected temperatures between 10 and 290 K in the region from 250 to 600 cm −1 of hydrogenated L-Ala [C3H7NO2, adapted from (Vik et al., 2005BB33)]. Note that, differently from D-Ala, the τ(NH3+) mode indicated for clarity by (*) in (b), does not split in L-Ala on cooling, as indicated by (+). However, on heating a remarkable wavenumber decrease accompanied by the increase in the linewidth, attributed to the increase in anharmonicity of the torsional vibrations, is observed in both samples.

IUCrJ
Volume 5| Part 1| January 2018| Pages 6-12
ISSN: 2052-2525
https://doi.org/10.1107/S2052252517015573