Vibrational spectra of S 7Se and a common force field for 34S 8, 32S 8 and S 7Se

Abstract

Raman spectra of solid S 7Se have been recorded both at room temperature and at low temperatures down to ~30 K. Abnormal half-widths of the low-temperature spectra compared with those of S 8 indicate that an ordered phase of S 7Se does not exist. Simultaneous calculations of a valence force field for 32S 8, 34S 8 and S 7Se yielded a refined force field for elemental sulphur along with the force constants of SSe bonds and SSeS angle deformations. The observed frequencies are reproduced to within 0.5% for all three molecules.