Quantum mechanical study of the high-temperature H+ + HD → D+ + H2 reaction for the primordial universe chemistry

Abstract

We use the time-independent quantum-mechanical formulation of reactive collisions in order to investigate the state-to-state H + + HD → D + + H 2 chemical reaction. We compute cross sections for collision energies up to 1.8 electron-volts and rate coefficients for temperatures up to 10000 kelvin. We consider HD in the lowest vibrational level v = 0 and rotational levels j = 0 to 4, and H 2 in vibrational levels v ′ = 0 to 3 and rotational levels j ′ = 0 to 9. For temperatures below 4000 kelvin, the rate coefficients strongly vary with the initial rotational level j, depending on whether the reaction is endothermic ( j ≤ 2) or exothermic ( j ≥ 3). The reaction is also found less and less probable as the final vibrational quantum number v ′ increases. Our results illustrate the importance of studying state-to-state reactions, in the context of the chemistry of the primordial universe.

HD–H+ collisions: statistical and quantum state-to-state studies

“…Such calculations are in principle very similar to those performed by Lepers et al 37 , 38 . However, the comparison between our results and those of Lepers et al 37 , 38 shows a systematic difference in the reactive rate coefficients of a factor of ∼ 2.…”

“…Such calculations are in principle very similar to those performed by Lepers et al 37 , 38 . However, the comparison between our results and those of Lepers et al 37 , 38 shows a systematic difference in the reactive rate coefficients of a factor of ∼ 2. This systematic difference arises from the consideration of the two H atoms as either distinguishable or indistinguishable particles 49 .…”

“…Indeed, the relative simplicity of the H + -H 2 collisional system and its isotopic variants represents a serious advantage for theoretical studies 23 . While the isotopic reaction D + + H 2 → HD + H + has been intensively studied, both experimentally [24][25][26] and theoretically [27][28][29][30][31][32][33] , only a few data is available for the reverse reaction HD + H + → D + + H 2 24,[34][35][36][37][38] .…”

“…Lepers et al 37,38 recently reported exact quantum timeindependent close-coupling (CC) calculations of the state-to-state rate coefficients for the HD-H + collisional system. In this work, however, they only focused on the reactive process, providing no rate coefficients for the excitation of HD through collisions with H + whereas such data are also very useful for astrophysical applications 14 .…”

Benchmarking an improved statistical adiabatic channel model for competing inelastic and reactive processes

“…All species involved, HD (X 1 Σ + ) and H 2 (X 1 Σ + g ), are in their electronic ground states, and competition between processes B1, B2 and B3 was accounted for in the statistical calculations. In contrast to the H + 3 isotopic variant discussed in III A, the insertion reaction for this system is slightly endothermic by ∼ 39.5 meV due to the difference in vibrational zero-point energies of H 2 and HD, and the different ionisation energies of H and D 43,44 .…”