Cross-sections exhibiting quantum resonances: the B+OH case

Abstract

Extensive theoretical quantum-mechanical calculations are reported for the cross-section and related dynamical quantities of the B+OH→BO+H reaction, on a previously developed potential-energy surface (PES) describing the ground electronic state. These calculations show, as an outstanding feature, the presence of marked structures in the shape of the excitation function as a consequence of the existence of a dense spectrum of rather long-lived resonance states. These are narrow enough to survive the angular momentum averaging, thanks to an important stabilization caused by an electronic minimum corresponding to a linear HOB configuration. The centrifugal barriers due to high values of the orbital angular momentum are found to lead to several orbiting shape resonances, as revealed by the opacity function plots and the dependence of the reaction probability on energy. Differential cross-sections corresponding to energies lying at either reactivity peaks or valleys in the integral cross-section show a highly symmetric dependence on scattering angle, indicating an important resonant contribution to reactivity in both cases. The possibility of directly observing resonances in experimental integral cross-section measurements is analysed in the light of the present results.