HIGH-PRESSURE STUDY OF THE FAR-INFRARED COLLISION-INDUCED ABSORPTION OF NONDIPOLAR LIQUIDS

Far-infrared collision-induced absorption of liquid benzene, hexafluorobenzene, and 1,3,5-trifluorobenzene were measured at pressures and room temperature with a synchrotron radiation source. The zeroth and second spectral moments of the absorption bands were obtained as a function of pressure. The collision-induced dipole moments and their time derivatives were obtained from the spectral moments for these liquids and previously measured carbon disulfide and carbon tetrachloride. The induced-dipole moments decrease with increasing pressure for the liquids studied except carbon disulfide for which the moment is nearly independent of pressure. This decrease in the moments is probably caused by increase in the cancellation effect of three-molecule correlation with an increase in pressure. The time derivatives of the collision-induced moments, on the other hand, increase with increasing pressure. This is explained by increase in collision frequencies with pressure. (C) 1995 American Institute of Physics.