INTERACTION-INDUCED RAMAN LIGHT-SCATTERING-STUDIES OF CH4 H-2 MIXTURES AS A FUNCTION OF DENSITY/

We have recently interrogated several binary supracritical mixtures by means of interaction-induced Raman light scattering originating from a probe molecule (supracritical methane) at a concentration of 10 mol % in a variety of supracritical solvent systems (e.g., Ar, CO2, CF4, e tc.). In this paper we look at a very different kind of solvent, supra critical molecular hydrogen. It was chosen because of its well-known r eorientational properties, i.e., quantum mechanical rotation in all ph ases (except perhaps metallic H-2(s)). The results indicate that the I /d vs d plots are more complicated than earlier systems studied and gi ve good evidence of additional numbers of H-2 molecules clustered arou nd the solute CH4. Hydrogen's absolute differential Raman rotational c ross-section for Delta J = 1 --> 3 is very well known and combined wit h the cross-section of the methane probe molecules' nu(1) symmetric st retching vibration, it was possible to quantify and compare the contri butions of various mechanisms known to be present in interaction-induc ed Raman light scattering of a wide variety of solvents and to therefo re judge their solvating capacities vis a vis CH4.