Photoionization for Na and Li cold atoms in a MOT

Summary form only given. Photoionization of cold atoms in their first excited state has been applied to measure the photoionization cross section in rubidium magneto-optical trap (MOT), and cesium MOT. The modifications of the MOT loading rate and of the steady state number of trapped atoms allow one to measure the dependence of the cold atom photoionization cross section on the laser wavelength for absorption from the excited atomic state. We report here on measurements of photoionization cross-sections of both laser-cooled sodium and lithium atoms at various photoionization wavelengths.