Couplings between molecular and crystal vibrational modes in imidazole have been investigated and the influence of the hydrogen bond on these modes has been studied. In normal-mode calculations a program has been used which allows all possible couplings between vibrations of the molecules and those of the crystal lattice. In this way molecular modes coupled to lattice vibrations and lattice modes describing predominantly hydrogen-bond vibrations have been isolated.The pOSitions of protons are then given by D, R, and . D is the distance of the H atom in the Xo direction,

No abstract

Raman and infrared spectroscopic studies of benzoic acid dimers and crystals have been made. Molecular and crystal normal modes have been calculated. An assignment of the observed spectra has been proposed and some specific modes discussed.

Raman ( 3 S 2 0 cm-') and IR (4000-80 cm-') spectra of benzophenone and a series of its puru-dkubstituted derivatives (substitoents F, C1, Br and CH,) as melts and in solution were recorded. A complete empirical a s s i p ment of tbe measured spectra was made and the influence of para substitution on tbe normal modes was investigated.

Raman and infrared vibrational spectra have been recorded for o-pbthalic acid as a single crystal, as a powder and in solution. The proposed assignment of the observed frequencies was made on the basis of a normal coordinate analysis and symmetry considerations of the crystal spectrum, which allowed the separation of internal vibrations of the A and B species.