TIME-RESOLVED STUDIES OF ULTRACOLD IONIZING COLLISIONS

Using 40 ns laser pulses, we probe the real-time dynamics of ultracold ionizing collisions in metastable xenon. We time resolve both shieldi ng and enhancement effects, and observe the production of Xe-2(+) mole cular ions through associative ionization. We estimate the rate of mol ecule formation in excited-state collisions, and directly measure the role of both flux enhancement and excited state survival in the collis ional enhancement process. Conceptually simple theoretical models are used to predict the dynamics of the collisional shielding.