State-to-state quantum dynamical study of H + Br₂ → HBr + Br reaction^†

The time-dependent wave packet method has been employed to calculate the state-to-state integral cross sections and differential cross sections (DCSs) for three initial states of the title reaction on the recently constructed neural network potential energy surface. It is found that the product HBr(υ′ = 2, 3, 4) states have the dominated population in the entire energy region considered here, indicating an inverted HBr vibrational state distribution. More than half of the available energy ends up as product internal motion, and most of which goes into the vibrational motion. Our calculations show that initial rotational excitation of Br₂ has little effect on the product ro-vibrational state distributions and DCSs of the reaction. While the initial vibrational excitation has some influences. The initial vibrational excitation to υ₀ = 5 obviously enhance the product vibrational excitation in the low energy region. The DCSs for collision energy up to 0.5 eV at the ground and rotationally excited state are peaked in the backward direction, but the width of the angular distribution increases considerably with the increase of collision energy. For the vibrationally excited state, the DCSs are rather complicated with some strong forward scattering peaks for highly vibrationally excited products.