Coherent control of bimolecular chemical reactions

We show how the method of coherent control can be applied to control product yield in bimolecular chemical reactions. First, a laser pulse prepares a coherent superposition of two bound levels of an electronically excited state of the reactants. Then, after a variable delay, a second laser pulse photodissociates the system to the ground state continuum. By varying the detuning of the excitation pulse and the delay between the two pulses, we show that significant control of the product ratio can be achieved. As a first application of the method we demonstrate, with exact quantum-mechanical calculations, the control of the collinear H+H2 and D+H2 reactions. The pulses and delays used in these calculations are on the order of picoseconds, a range of time scales well within that achievable with conventional laser systems.