Collimation of a beam of caesium atoms by optical molasses, with resulting reduction in longitudinal beam velocity

摘要

We report on the collimation of a beam of caesium atoms by a one- or two-dimensional σ~(+)-σ~(-) optical molasses installed transverse to the atomic-beam direction. The width of the spatial distribution of atomic beam was reduced from 15 to 2 mm. We found that the collimation process strongly affects the longitudinal velocity; after collimation the mean of longitudinal velocity was reduced within a finite detection area. This result is due to longitudinal velocity selection by the collimation process. A computer simulation based on the two-photon laser-cooling theory was made, and the results were in a good agreement with the experiment.