Collisional relaxation and internal energy redistribution in NO2 investigated by means of laser-induced thermal grating technique

Optical scattering from laser-induced thermal gratings (LITGs) was employed in investigations of molecular relaxation processes in gas mixtures contai ning a small amount of NO2 diluted with different buffer gases (N-2,Ar, CO2 ). The thermal gratings were generated by the thermalization of the molecul ar internal energy stored in the NO2 molecules after laser resonant excitat ion of the B-2(I) <-- (2)A(1) Huber-Douglas band. The temporal evolution of LITGs was detected by scattering a cw read-out laser beam. A theoretical s imulation of experimental results was performed in which the linearized hyd rodynamic equations relevant to collisions responsible for the relaxation p rocess were solved by following a two-step rate equations approach. (C) 200 0 Elsevier Science B.V. All rights reserved.