HIGH-RESOLUTION INFRARED-SPECTRA OF THE NU(3) VIBRON IN NATURAL SULFUR AND IN THE ISOTOPICALLY PURE S-32 CRYSTAL

We have studied by high resolution infrared spectroscopy the v(3) vibr on band in natural and isotopically pure S-32 sulfur crystals. From th e comparison of the spectra we have assigned the bands due to-the diff erent molecules containing one or two atoms of S-34 as well as one ato m of S-33. We have measured tl;e bandwidth and the frequency of the vi bron as a function of temperature from 10 to 140 K both in the natural and in the isotopically pure crystal and we have interpreted the resu lts in terms of decay and scattering processes. In particular we have explained the nonlinear evolution of the bandwidth and of the frequenc y shifts with temperature in terms of scattering processes controlled by quartic terms of the crystal Hamiltonian.