High‐pressure Raman spectra of deuterated <scp>L</scp>‐alanine crystal

Abstract

Abstract Raman spectra of deuterated L ‐alanine have been obtained at high‐pressure conditions. A phase transition at ∼1.5 GPa associated with the splitting of some internal modes and increase of the wavenumber of the external modes was observed. Similarly to the hydrogenated L ‐alanine crystal, this first transition was related to a symmetry change. Moreover, further modifications of the Raman spectra were observed at 4.4 GPa, which may be associated to conformational changes of the molecule. To give further support to such a hypothesis, neutron powder diffraction measurements were performed. Information about the cell parameter at atmospheric pressure gave valuable information about the ND distances, shedding light on the behavior of the torsional vibration of ND 3 + . Copyright © 2009 John Wiley &amp; Sons, Ltd.