Abstract
We present the non-adiabatic, conical-intersection quantum dynamics of the title collision where reactants and products are in the ground electronic states. Initial-state-resolved reaction probabilities, total integral cross sections, and rate constants of two H2 vibrational states, v0 = 0 and 1, in the ground rotational state (j0 = 0) are obtained at collision energies Ecoll ≤ 3 eV. We employ the lowest two excited diabatic electronic states of and their electronic coupling, a coupled-channel time-dependent real wavepacket method, and a flux analysis. Both probabilities and cross sections present a few groups of resonances at low Ecoll, whose amplitudes decrease with the energy, due to an ion-induced dipole interaction in the entrance channel. At higher Ecoll, reaction probabilities and cross sections increase monotonically up to 3 eV, remaining however quite small. When H2 is in the v0 = 1 state, the reactivity increases by ~2 orders of magnitude at the lowest energies and by ~1 order at the highest ones. Initial-state resolved rate constants at room temperature are equal to 1.74 × 10−14 and to 1.98 × 10−12 cm3s−1 at v0 = 0 and 1, respectively. Test calculations for H2 at j0 = 1 show that the probabilities can be enhanced by a factor of ~1/3, that is ortho-H2 seems ~4 times more reactive than para-H2.
Highlights
Atomic Hydrogen and Helium are the dominant chemical species of the early Universe (Galli andPalla, 2013) and of the interstellar medium, and are ionized by cosmic rays
We have taken into account the non-adiabatic conical intersection (CI) coupling between the first two excited diabatic potential energy surface (PES) of HeH+2
Dynamical calculations are performed for the ground and first excited vibrational states of H2, for investigating vibrational effects on the DCT dynamics, and collision energies up to 3 eV are considered
Summary
Atomic Hydrogen and Helium are the dominant chemical species of the early Universe (Galli andPalla, 2013) and of the interstellar medium, and are ionized by cosmic rays. A few works have theoretically investigated the dynamics of the DCT collision since 1994, when Aguillon (1994) employed a semiclassical coupled wavepacket (WP) method and the analytical diabatic PESs of Aguado et al (1993) for computing ICSs for ground and excited vibrational states v0 of H2, up to v0 = 4 and in the Ecoll range from 2 to 10 eV.
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