Quantum mechanical study of the high-temperature $\mathrm{H}^+ +
  \mathrm{HD} \to \mathrm{D}^+ + \mathrm{H}_2$ reaction for the primordial
  universe chemistry
  We use the time-independent quantum-mechanical formulation of reactive
collisions in order to investigate the state-to-state $\mathrm{H}^+ +
\mathrm{HD} \to \mathrm{D}^+ + \mathrm{H}_2$ 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
($j\le 2$) or exothermic ($j\ge 3$). 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.
