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Micro‐conformational transitions in L ‐alanine single crystals revisited by low wavenumber Raman spectroscopy
Author(s) -
Kolesov Boris A.,
Boldyreva Elena V.
Publication year - 2011
Publication title -
journal of raman spectroscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.748
H-Index - 110
eISSN - 1097-4555
pISSN - 0377-0486
DOI - 10.1002/jrs.2768
Subject(s) - raman spectroscopy , wavenumber , zwitterion , crystallography , chemistry , hydrogen bond , physics , optics , molecule , organic chemistry
The properties of the crystalline L ‐alanine have been attracting attention for a very long time, and there is much controversy in the results already reported. One of the most interesting problems is that of the localization of vibrational energy and the micro‐transitions (named ‘breathers’ by Barthes et al. [M. Barthes, H. N. Bordallo, F. Dénoyer, J.‐E. Lorenzo, J. Zaccaro, A. Robert, F. Zontone, Eur. Phys. J. 2004, B37 , 375]. In the present study, we have addressed this problem once again, having measured the high‐resolution polarized Raman spectra in the temperature range from 4 to 300 K. The wavenumber, bandwidth and intensity of all the modes polarized along the c ‐axis (the axis of the head‐to‐tail chains of zwitterion in the structure) show discontinuities at 30–50, 100–120 and 180–220 K. We interpret the observed anomalies of spectral characteristics in terms of micro‐conformational transitions accompanied by the rearrangement of the hydrogen‐bond network and relate them to previously published work. Copyright © 2010 John Wiley & Sons, Ltd.