Effect of laser radiation on the mobility of electrons in gases

Numerical solutions of Boltzmann's equation are obtained for the distribution of electrons in gaseous Ar in the presence of a dc electric field and a laser field. The calculations are performed at field strengths below those either of electrical or optical gas breakdown in order to study the effect of the radiation on dc-field-induced electron mobilities. The isotropic component of the electron distribution function oscillates with energy as a result of the discrete nature of free-free absorption and stimulated emission. Similar structure has been observed in previous studies at laser-field strengths close to optical breakdown with no dc field present. The radiative processes cause the mobility to increase by roughly the same amount as that obtained by use of the classical model of microwave electron heating, or by removing the laser and increasing the temperature to a thermal energy close to one laser photon. Thus, the energy oscillations in the distribution are not significantly probed by the $e$,Ar mobility. These findings suggest the use of molecular gases, having vibrationally inelastic-threshold energies in the region of oscillations, to find mobilities more sensitive to the discrete nature of the radiative processes.