Laser cooled rubidium atoms in the 5D5/2 level: Excitation, photoionization and collisions

Date of Completion

January 2001


Physics, Atomic




A series of experiments is performed on cold 85Rb atoms confined in a magneto-optical trap. A variation of Stimulated Raman adiabatic passage (STIRAP) is used to transfer population from the 5S 1/2 ground state to the 5D5/2 state with an efficiency exceeding 80%. This process relies on moderately intense pulses arriving in the counterintuitive order, i.e., the upper transition (5P → 5D) driven before the lower transition (5S → 5P ). There is reasonable agreement with computer simulations, excepting a marked discrepancy between measured intensities and those used in the simulations. With a large ensemble of 5D atoms available, the 5D photoionization cross section at four different laser wavelengths (1064, 788, 647 and 532 nm) is determined via trap loss measurements. The theoretical calculations agree well with the experimental results (17.7, 10.9, 7.6 and 5.2 Mb, respectively). An experiment to measure the 5S-5D collisional rate constant sets an order-of-magnitude upper bound of 10−10 cm3/s, assuming all atoms are 5S-5D pairs. ^