Modeling quantum dynamics of photodetachment from closed-shell anions: Static versus fluctuating well-depth models

The electronic states of halide ions are modeled by a one-dimensional Hamil tonian with a potential V(x) = -V(0)e(-sigma x2). The two parameters V-0 an d sigma are fixed by requiring V(x) to reproduce the experimentally observe d ground-state ionization potentials of the halide ions concerned. The pote ntials so generated are shown to support only one bound state in each case. The time-dependent Fourier grid Hamiltonian method is used to follow the i onization dynamics in monochromatic light of fairly high intensities. The t otal Hamiltonian, in the most general case, reads H(t) = P-x(2)/2m - V(0)e( -sigma x2) - epsilon(0)s(t)ex sin(omega t). For pulsed fields [s(t) = sin(2 )(pi t/t(p))], the computed ionization rate constants are seen to increase with increase in the peak intensity (epsilon(0)) of the electric field of l ight. The possibility of additional transient bound states being generated at the high intensities of light and its possible consequences on the obser ved ionization rates are explored. The environmental effects on the dynamic s are sought to be modeled by allowing the well depth (V-0) to fluctuate ra ndomly [V-0(t) = V-0 + Delta VR(t); R(t) randomly fluctuates between +1 and -1 with time, Delta V is fixed]. The ionization rate constants (k(epsilon) ) are shown to be significantly affected by fluctuations in V, and pass thr ough a well-defined minimum in each case for a certain specified frequency of fluctuation. An alternative model potential V(x) = -V(0)e(-sigma x) is a lso shown to yield similar results. (C) 1999 John Wiley & Sons, Inc.