Coherent radiative control of molecular reaction dynamics: Phase-controlled photodissociation of HOD

We present experiments and calculations on the coherent control of product branching ratios in a reaction with multiple, chemically distinct product channels. Our goal is to drive a reaction to a desired end product that is not necessarily favored either statistically or energetically. Our first application is to the photodissociation of isotopically substituted water, HOD. We employ a laser field consisting of a fundamental and its third harmonic (608 and 203 nm) with a selected phase relationship to photodissociate state-selected HOD(v, J) molecules. Detection of the OH and OD products by laser induced fluorescence allows us to determine which bond was broken in the reaction. In parallel with our experimental efforts we are performing time-dependent, wave packet calculations of the dynamics of this reaction. The results of our experiments and calculations show that selectivity in the OH/OD branching ratio can be achieved, even when both channels are energetically accessible