Light can induce thermodynamic and hydrodynamic fluxes in a gas, which reflect the light-induced modifications of the velocity distribution of the gas particles. The common condition for these effects to occur is the combination of velocity-selective radiative excitation with state-dependent gas-kinetic cross sections. It has recently been suggested that gas-kinetic effects of light in a molecular gas can also arise without state-dependent total cross sections, due to rotational inelastic collisions. Standard gas-kinetic techniques are not directly applicable in this case, since the rapid processes do not drive the system to a steady state. We give a generalization of the standard formalism so as to encompass this case. We apply this generalized formalism in the simplest model case of three-state particles.

• Received 21 August 1991

DOI:https://doi.org/10.1103/PhysRevA.44.7615