Session J15 - Poster Session II.
POSTER session, Sunday morning, April 20
Congressional Hall, Renaissance
A nonlinear absorption is observed when an atomic transition is saturated. This intensity dependent absorption was measured on the D_1 line in atomic cesium. The spatial cross section of the laser beam and the magnetic field applied to the vapor were controlled and varied during data collection to manipulate the transit relaxation and magnetic sublevel mixing rates, respectively. A three-level rate equation model does not successfully reproduce the data obtained in the absence of a magnetic field. Hence, a more complex and complete model that explicitly includes all of the hyperfine magnetic sublevels (a multilevel model) and accurately models all of the data is presented. The good agreement between this model and the data allows the determination of the transit relaxation rate (due to atomic time of flight through the laser beam), \Gamma_t=(1.13\pm0.20)v_rms/D, where v_rms is the two-dimensional rms speed of the atom and D is the beam FWHM.