VIBRATIONAL DEPHASING IN H-2 AND HD DISSOLVED IN LIQUID AND HYPERCRITICAL ARGON

Lineshape data have been obtained for the isotropic Raman spectra of H D and para H-2 diluted in liquid and hypercritical argon. The observed profiles near 2rho(c), are interpreted in terms of pure vibrational d ephasing and fast modulation process. In the critical region an inhomo geneous broadening is observed; it is superimposed in the HD case, on a rotational contribution. A detailed analysis of the Q spectra obtain ed for the normal H-2-argon system along the critical isochore provide s evidence for the role of density fluctuations near the liquid-gas cr itical point.