Three laser experiments in gases

Three laser experiments performed in gases are reported. Four wave degenerate mixing in cesium vapor is described. Its basis in nonlinear optics is explained and a simple set of equations are derived, which predict the resonant behavior, density dependence, and the power dependence of the signal. Inelastic scattering cross sections for the 9D and 10D states of cesium were measured. The observation of cancellation of rotational effects in the intensity of ultraviolet bands of OH are reported. The band oscillator strength for transition in the band of OH was measured and was independent of rotational excitation. This independence is explained in terms of the cancellation of a rotationally induced increase in the Franck-Condon factor by an equivalent decrease in the electronic transition moment.