- 2 - Laser Studies of Relaxation Processes in Sf

The infrared spectroscopy of SF6 relevant to laser experiments is discussed. A computed contour of the v3 band is presented which reproduces the prominent Q branch structure. Experiments measuring the saturation of absorption by the v3 transition in SF6 by a CW CO, laser and Q-switched pulse transmission in the same medium are described. The results of these experiments are interpreted with the aid of a four state model for energy transfer in SF Machine calculations based on this model reproduce the experimental results and yield cross sections for rotational and vibrational energy transfer. A double resonance experiment involving two CO2 lasers which allows the direct, time resolved observation of ground state bleaching, and excited state absorption in SF6 is described. The experimental results yield rates of vibrational to translational energy transfer in bimolecular collisions between SF6 and a variety of buffer gases and provide evidence for the validity of the four state model. Finally the direct observation of acoustical pulses generated in SF6 gas by a coincident Q-switched CO2 laser is reported. Measurements on these pulses enable us to set a lower limit on the rate at which translational energy is generated in the gas when the laser pumped levels relax. Thesis Supervisor: Jeffrey I. Steinfeld Title: Associate Professor of Chemistry