Quantum theory of laser catalysis in one and three dimensions

Abstract

A theory of the laser catalysis of the H + H₂ exchange reaction in the collinear configuration and in three dimensions is presented. The collinear H + H₂ system in a strong laser field is treated by a method composed of a converged coupled channels expansion for the non-radiative processes, coupled with an exact partitioning technique for the interaction with the radiation. The method enables computations to be performed for an arbitrary number of field-intensities with very little effort beyond that required for a single-intensity computation.

By studying the optical reactive line-shapes as a function of the scattering energy, the signature of the scattering resonances on optically induced reaction is unravelled. It is shown that when the collision energy is tuned to a resonance, laser catalysis results in selective vibrational excitation of the product H₂ molecule. Implications of this effect for past and future experiments are discussed.

A three-dimensional theory based on the same exact partitioning technique is then presented. In this case, the bound–free scattering amplitudes, which serve as input to the theory, are obtained by assuming separability in terms of a hindered-rotor vibrationally adiabatic basis. We use the theory to compute reactive differential and integral laser-catalysis cross-sections. We study the laser intensity dependence of the reactivity, the role played by isolated and overlapping power-broadened resonances and how the angle of the relative velocities of the reagents affects the reactivity.