High-pressure Raman study of l-alanine crystal

Single-crystal samples of l-alanine, CH 3CH(NH 2)COOH, a fundamental amino acid of most proteins, have been studied by Raman spectroscopy in a diamond-anvil cell up to pressures of 43 kbar. From the analysis of results we observed that the crystal undergoes a phase transition about 22–23 kbar. The transition is accompanied by abrupt changes in the relative intensity of low-energy bands, by the appearance of a phonon in the external mode region of the spectrum and by some modifications in phonons of the internal mode type.