FRICTION AND DIFFUSION-COEFFICIENTS FOR COOLING OF ATOMS IN LASER FIELDS WITH MULTIDIMENSIONAL PERIODICITY

Methods are presented that allow numerical calculations of the friction and momentum diffusion coefficients for atomic motion in laser fields with periodicity in one, two, and three dimensions. Polarization gradients in the fields lead to increased friction on atoms with a Zeeman sublevel structure, and new features arising in the cases of motion in two and three dimensions are discussed. There is a marked position dependence of the calculated quantities, and the consequence for the forces on atoms following specified trajectories is studied. Temperatures determined from the position-averaged friction and diffusion coefficients scale with the laser power divided by the frequency detuning, except in some special configurations. Of relevance for experiments on cooling, the relative merits of four different laser configurations in three dimensions are studied.