MULTIPLE ABSORPTION AND RELAXATION PROCESSES IN SF6-CH4 MIXTURES - ANEXPERIMENTAL-STUDY

The effects of collisions with nonabsorbing partner molecules (CH4) we re investigated in absorption processes in SF6 irradiated by a pulsed CO2 laser. An experimental apparatus was developed for simultaneous ab sorption measurements both by transmission and photoacoustic spectrosc opy. Enhanced absorption cross sections of SF6 in collisions with nona bsorbing CH4 molecules were measured, together with the average number of absorbed photons per molecule. The differential absorption cross s ections were also determined for the fluence range of 0.1-0.7 J/cm(2), and the CH4 pressure range of 1-140 mbar. The results obtained were a nalyzed based on the predictions of the generalized two-level model pr oposed for multiple photon processes. An estimate of the role that rot ational-rotational and vibrational-translational relaxation processes play, in inducing the effect of enhanced absorption in SF6-CH4 mixture s irradiated by pulsed CO2 laser radiation, is given.