Light-induced drift of aerosol particles in gas mixtures

We analyze the motion of an aerosol particle in a gas mixture in which the molecules of one of the components have been selectively excited as to velocity by resonant optical radiation. We derive expressions for the force with which the gas acts on the particle and for the velocity of particle motion in the Knudsen regime. We also examine the dependence of the force and velocity of photophoresis on the offset of the radiation frequency from the center of the absorption line and on the concentration and mass ratios of the molecules of the absorbing and buffer gases.