Relaxation processes in singlet O-2 analyzed by laser-induced gratings

Thermal laser-induced gratings have been generated in mixtures of oxygen wi th other gases by the formation of a rotational state thermal equilibrium a fter the excitation of the O-2 molecules to the singlet b(1)Sigma(g)(+)(nu' = 0) state. The sign and the amount of energy transfer in the formation of the rotational state thermal equilibrium are determined by measuring the p hase in the oscillation of the diffraction efficiency of the grating. The v alues are compared with values, which were calculated assuming a Boltzmann distribution in the rotational states. Furthermore, the effect from the slo wer vibrational and electronic relaxation processes on the first stage on t he grating formation is calculated and compared with the experimental findi ngs. (C) 2000 Elsevier Science B.V. All rights reserved.