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

Abstract

The electronic states of halide ions are modeled by a one-dimensional Hamiltonian with a potential V(x)=-V₀e-σx². The two parameters V₀ and σ are fixed by requiring V(x) to reproduce the experimentally observed ground-state ionization potentials of the halide ions concerned. The potentials 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 ionization dynamics in monochromatic light of fairly high intensities. The total Hamiltonian, in the most general case, reads H(t)=P_x²/2m-V₀e-σx²0_s(t)ex sin(ωt). For pulsed fields [s(t)=sin²(πt/t_π)], the computed ionization rate constants are seen to increase with increase in the peak intensity of the electric field of light. The possibility of additional transient bound states being generated at the high intensities of light and its possible consequences on the observed ionization rates are explored. The environmental effects on the dynamics are sought to be modeled by allowing the well depth (V₀) to fluctuate randomly [V₀(t)=V₀+δVR(t); R(t) randomly fluctuates between +1 and -1 with time,δV is fixed]. The ionization rate constants (k₀) are shown to be significantly affected by fluctuations in V₀ and pass through a well-defined minimum in each case for a certain specified frequency of fluctuation. An alternative model potential V(x)=-V₀e^-σx is also shown to yield similar results.