Multiple absorption and relaxation processes in SF6CH4 mixtures: an experimental study Original Research Article

The effects of collisions with nonabsorbing partner molecules (CH4) were investigated in absorption processes in SF6 irradiated by a pulsed CO2 laser. An experimental apparatus was developed for simultaneous absorption measurements both by transmission and photoacoustic spectroscopy. Enhanced absorption cross sections of SF6 in collisions with nonabsorbing CH4 molecules were measured, together with the average number of absorbed photons per molecule. The differential absorption cross sections were also determined for the fluence range of 0.1–0.7 J/cm2, and the CH4 pressure range of 1–140 mbar. The results obtained were analyzed based on the predictions of the generalized two-level model proposed for multiple photon processes. An estimate of the role that rotational-rotational and vibrational-translational relaxation processes play, in inducing the effect of enhanced absorption in SF6CH4 mixtures irradiated by pulsed CO2 laser radiation, is given.