THE FAST BETA-PROCESS IN M-TRICRESYL PHOSPHATE AND ITS POSSIBLE CONNECTION WITH THE BOSON PEAK - A LIGHT-SCATTERING ANALYSIS

A wide frequency range and high-resolution light scattering study on t he molecular fragile glass former m-tricresyl phosphate was performed. The depolarized spectra were considered as consisting of a quasielast ic central line, the transverse acoustic Brillouin component (not disc ussed here) and the boson peak (BP). The central line width follows ve ry closely the values known from a nuclear magnetic resonance experime nt, which measured the molecular reorientation, that is the alpha proc ess. The BP was considered to result at least partly from density fluc tuation. We apply a hydrodynamic description to its temperature depend ence, where the parameters are known from a longitudinal acoustic Bril louin scattering experiment. Thus one can successfully describe the BP as well as the region between the central line and the BP, including the considerable change in spectral shape. The relative weights of alp ha and beta processes show a temperature dependence as is often found in mode-coupling theory. The width parameter for the beta process show s only a slight temperature dependence and differs between the Brillou in and BP descriptions by a factor of only two to three.