Kinetics of two-level atom radiation

A. Muriel

Françoise Hénin, Michel De Haan

G J Papadopolos

Arturo Bambini

The transfer of energy from the translational to the internal degrees of freedom or vice versa is analyzed for radiatively assisted inelastic collisions among atoms in a gas. For a specific atomic-level configuration, it is shown that the absorption of a laser photon may induce a transition between two levels that are displaced by the collisional interaction (a dipole-dipole potential in this treatment) if a fraction of the kinetic energy of the atomic relative motion is simultaneously absorbed. The process thus results in a cooling of the atomic kinetic temperature. In other level configurations, energy goes in the opposite direction, with a heating of the kinetic temperature. This mechanism is described by means of the Wigner-function formalism, which allows a passing to the quasiclassical limit for the atomic motion in a simple way.

José Tito Mendonça, A. Serbêto

We study the collective scattering of radiation by a large ensemble of Na≫1 atoms, in the presence of a pump field. We use the wave-kinetic approach where the center-of-mass position of the moving atoms is described by a microscopic discrete distribution, or alternatively, by a Wigner distribution. This approach can include thermal effects and quantum recoil in a natural way, and even consider atomic ensembles out of equilibrium. We assume two-level atoms with atomic transition frequency ωa very different from the frequency ω0 of the pump field. We consider both the quasi-classical and quantum descriptions of the center-of-mass motion. In both cases, we establish the unstable regimes where coherent emission of radiation can take place.

Daniel F. Walls, Gerard J Milburn