Comparing abstraction and exchange channels in the H + HBr reaction: A stereodynamical control perspective.

Abstract

This study investigates the stereodynamical control of the H + HBr (v = 0, j = 1) reaction within 0.01-1.50 eV collision energy using the time-dependent wave packet method. The key findings reveal a clear β-dependent (β is the angle of alignment) scattering behavior: the β = 90° configuration in the abstraction channel enhances reactivity and dominates the formation of the products at lower vibrational states with increasing collision energy. In contrast, the β = 0° configuration promotes all vibrational states in the exchange channel. Notably, the β = 45° configuration displays the smallest cross sections in both channels due to destructive quantum interference, contrasting with the constructive interference in the β = 90° configuration. Channel competition analysis demonstrates that β = 0°/45° configurations enhance exchange channel dominance, whereas β = 90° favors the abstraction channel. The differential cross section shows that the products in the abstraction channel shift from backward to forward in the β = 0°/45° configuration, while maintaining sideways distributions in the β = 90° configuration, and in the exchange channel, it is always backward scattering. The highest reaction rate in the abstraction channel occurs at the parallel alignment in the temperature region between 200 and 1000 K.