Effect of phase memory under collisions on field work and light-induced drift of gas particles

Abstract

The influence of phase memory under collisions on the field work and the light induced drift (LID) effect of two-level gas particles is studied. It is shown that the phase memory effects may lead to the case where about half of the particles interacting with radiation amplify the incident radiation. The integral absorption coefficient for this remains positive due to growing radiation absorption by another half of the particles. It has been found that the phase memory strongly affects the LID under v ≫ kv̄ (v is the collision frequency, kv̄ is the Doppler line width): calculation of LID without regard for the phase memory can lead to underestimation of the LID effect value by a factor of (v/kv̄)2 ≫ 1. Interaction of the particles in the hard sphere model is used to illustrate that the phase memory begins to affect the LID when the relative difference of the transport cross-sections of the particles is ground and excited states is small: Δσ/σ ≲ λ̄/R, where λ̄ is the de Broglie wavelength at thermal velocities, R is the sphere radius.