Initial state laser control of curve-crossing reactions using the Rayleigh-Ritz variational procedure

A new two-step procedure for laser control of photodissociation is presented. In the first step of the procedure, we show that control of photodissociation product yields can be exerted through preparation of the initial wave function prior to application of the photodissociation field in contrast to previous laser control studies where attention has focused on the design of the field which induces dissociation. Specifically, for a chosen channel from which maximum product yield is desired and a given photodissociation field, the optimal linear combination of vibrational eigenstates which comprise the initial wave function is found using a straightforward variational calculation. Any photodissociation pulse shape and amplitude can be assumed since the Schrodinger equation is solved directly. Application of this method to control of product yields in the photodissociation of hydrogen iodide is demonstrated. The second step of the control procedure involves the preparation of the coherent superposition of discrete levels obtained from the previous step; design of the preparatory field can be done analytically for two or three level systems as demonstrated here or with other well-studied iterative field design methods. (C) 1996 American Institute of Physics.