Pulse-probe measurements in the v3band of SF6at low temperature and low pressure

To improve understanding of multiple-photon absorption by polyatomic molecules, we have performed a series of experiments wherein a pulsed CO2laser irradiated 0.02-0.08 torr samples of SF6at 145 K. A CW probe laser monitored the time response of the induced absorption or transmission at many CO2laser lines that are in or near the ν3absorption band of SF6. The experiments covered a 40-fold fluence range and probe times out to 4 ms. We conclude that the absorbed laser radiation produces a nonthermal vibrational-energy distribution and that intermolecular vibrational-energy transfer is important at early times in redistributing the absorbed energy. We also discuss the influence of other processes on the induced spectrum.