BROKEN DYNAMICAL SYMMETRY CONDITION TO CONTROL A CHEMICAL-REACTION BYTHE COMPLEX COORDINATE (T,T') METHOD

Using the (t, t') formalism [J. Chem. Phys. 99 (1993) 4590] combined w ith the complex coordinate method, exact (i.e. not perturbative) condi tion for control of a model chemical reaction is derived regardless of the field intensity and whether the electromagnetic field is time-per iodic or not. We prove that upon breaking the dynamical symmetry H(p, x, t)= H(-p, -x, t + T/2), the dissociation channel of the A + BA <-- ABA --> AB + A reaction can be controlled. It is shown that when the m olecular/field interaction is given by ($) over cap p(z)f(t), where f( t) represents the electromagnetic field, the dissociation channel of t he A + BC <-- ABC --> AB + C reaction can be controlled by breaking th e dynamical symmetry property, f(t) = -f(t + T/2). For time-periodic f ields T is the time period (i.e. one optical cycle) where for pulsed l asers it is the duration of the pulse. Numerical examples are given fo r symmetric and asymmetric model Hamiltonians subjected to two cw lase rs. These numerical examples illustrate the role of the phase differen ce between the cw lasers, regardless of the laser intensity, in the co herent control procedure which was first proposed by Brumer and Shapir o [Chem. Phys. Letters 126 (1986) 54].