Nonadiabatic Dynamics and Rotational Coupling in $\mathrm{He}{\mathrm{H}}^{+}$ Dissociative Recombination and Resonant Ion-Pair Formation

Abstract

We present a time-dependent wave-packet study of dissociative recombination (DR) and resonant ion-pair (RIP) formation in $\mathrm{He}{\mathrm{H}}^{+}$ isotopologues. Nuclear dynamics are treated on a manifold of 23 coupled electronic states of ${}^2\Sigma$, ${}^2\Pi$, and ${}^2\Delta$ symmetries, including rotational couplings between different symmetries. The results reveal that inclusion of a large manifold of resonant states and rotational couplings significantly enhances the DR cross section relative to earlier theoretical studies. In the diabatic representation, ${}^2\Sigma$ states dominate the recombination dynamics, while in the adiabatic representation, ${}^2\Pi$ and ${}^2\Delta$ states contribute significantly at low collision energies. For RIP formation, two different diabatization schemes yield systematically larger cross sections than previous models, highlighting the sensitivity of ion-pair production to electronic coupling structure. Isotopic effects are examined, showing a clear inverse dependence of cross section magnitude on reduced mass. Thermal rate coefficients are computed over $10^2$ to $2\times 10^4$ K thermal electron temperatures. Isotopic effects are examined, showing a clear inverse dependence of cross section magnitude on reduced mass. The results are compared with rotational-state-resolved experimental and theoretical results. The present results highlight the importance of multistate coupling and rotational interactions in electron-driven fragmentation processes relevant to primordial and astrophysical plasmas.

11 pages and 8 figures. arXiv admin note: text overlap with arXiv:2301.03893