Pathway for two-color photoassociative ionization with ultrafast optical pulses in a Rb magneto-optical trap

Ultrafast and narrow linewidth lasers are combined to study multiphoton photoassociative ionization (PAI) in a Rb magneto-optical trap. Through the use of time of flight spectroscopy and by varying the parameters of the ultrafast laser, the excitation pathway for PAI was determined. It was found that Rb-2(+) is formed, not by direct photoionization, but by sequential excitation of Rb-2 to an autoionizing state. Determining the excitation and ionization pathway was a necessary first step for future efforts in trying to establish coherent control techniques, first for the efficient production of translationally cold Rb-2, and then for transferring population to a desired vibrationally cold molecular state.