Short time-scale effects in the pulsed source thermal lens

The pressure and density disturbances which develop in a gas after the absorption of a short laser pulse of gaussian radial profile have been analysed in terms of the characteristic times for pressure wave propagation and vibrational-translational energy transfer for the absorber molecules. The relative time scales of other processes affecting the disturbance have also been considered. Experimental results, in which the non-homogeneous density field is detected by the thermal lens effect on a second, continuous mode, probe laser, are presented. The results are compared with the theoretical predictions and an attempt is made to extract rate constants for the SF6/cyclopropane energy transfer process.