T1 Relaxation of Perylene in Fluid Ethane: Pressure-Dependent Changes in Short-Range Organization

Abstract
We report our measurements of vibrational population relaxation of the v7 (1375 cm−1) mode of perylene in ethane at a series of fluid pressures. The data show that T1 decreases with increasing fluid pressure and that the dependence of T1 on pressure is not consistent with predictions based on simple spatial or stoichiometric considerations. The data indicate a nonrandom orientational distribution of the solvent molecules about the solute where the portion of the solvent environment sensed by the perylene v1 coordinate changes from one ordered state to another ordered state with increasing pressure.