Coherent control of multiphoton-ionization passage of excited-state rubidium atoms

Abstract

We have investigated multiphoton-ionization passages of rubidium atoms initiated from the excited 5P(3/2) energy state. For this we used coherent control schemes based on femtosecond laser pulse shaping applied to cold atoms spatially isolated in a magneto-optical trap. With programed laser pulses of spectral pi-phase step, of which location was varied within the laser spectrum, the sequential two-photon-ionization passage along the 5P(3/2)-5D continuum was probed in terms of trap-loss spectroscopy. The coherent control two-photon-ionization method unveiled not only the resonantly enhanced two-photon ionization but also the asymmetric nature of the ionization profile structure given as a function of the spectral phase step location. Experimental results show good agreement with the second-order perturbation calculation of the constituent possible ionization passages.