Polarized Raman spectra and intermolecular potential of DL ‐alanine crystal

Polarized Raman spectra of DL‐alanine and N‐deuterated DL‐alanine single crystals have been recorded. A normal coordinate analysis has been made for the optical active intra‐ and intermolecular vibrations of DL‐alanine crystal. As in the case of L‐alanine crystal, large factor group splittings were observed for the CH3 asymmetric deformation mode. The magnitudes of the observed splittings are elucidated well by the empirical potential function of the exp‐6 type for the non‐bonded atom‐atom interaction. The differences in the NH3 rocking and the CH3 rocking frequencies between L‐ and DL‐alanine crystals are ascribed to the differences in the intermolecular potential and the molecular geometry, respectively. A good agreement was obtained between the observed and the calculated lattice frequencies.