MACROSCOPIC STATE OF GASES IN A LIGHT-FIELD

We consider a gas or a gas mixture in a radiation field. The microscopic evolution equations for the distribution functions for the various particle states are separated into a rapid and a slow time scale. This separation defines the relevant quantities that specify the macroscopic state of the system. The evolution equations for the macroscopic variables take the form of a modified diffusion equation in the case of a dilute vapor in a buffer gas, and of generalized Navier-Stokes equations for a single-component gas. The equations contain light-induced fluxes as source terms, and the transport coefficients are modified by the light.