Professors Kleiber, Stwalley, and Sando are supported by the Experimental Physical Chemistry Program in a collaborative experimental and theoretical investigation of far-wing laser absorption leading to chemical reaction and various inelastic processes in alkali metal interactions with hydrogen molecules. The far wing absorption technique is one way in which to probe directly the properties of the usually very short-lived intermediate or transition region between reactants and products in a chemical transformation. A laser tuned slightly off-resonance from an allowed or a forbidden atomic transition of an alkali metal is being used to pump colliding alkali-hydrogen "intermediates" at distances suitable for resonant absorption of the off-resonance photon. The subsequent branching into various product channels is monitored, as a function of the amount of laser detuning, by either emission measurements or laser-induced fluorescence. Of particular interest are reactions dynamics near threshold and the influence of spin-orbit coupling on the dynamics. Theoretical treatments are emphasizing approximate classical path methods that include the full motion of the nuclei. Extensions and generalizations of semiclassical line-broadening theories are being explored.
