Breakup of H$_2^+$ by photon impact

TL;DR

This paper presents precise calculations of the breakup cross sections of H$_2^+$ by photon impact, distinguishing between dissociative excitation and ionization, and compares exact results with approximate methods.

Contribution

It provides the first exact nonadiabatic calculations of H$_2^+$ breakup cross sections, evaluating the accuracy of Born-Oppenheimer approximations.

Findings

Converged cross sections span six orders of magnitude.

Born-Oppenheimer approximation is surprisingly accurate.

Using Born-Oppenheimer final states near threshold causes pathologies.

Abstract

Total and partial cross sections for breakup of ground rovibronic state of H$_2^+$by photon impact are calculated using the exact nonadiabatic nonrelativistic Hamiltonian without approximation. The converged results span six orders of magnitude. The breakup cross section is divided into dissociative excitation and dissociative ionization. The dissociative excitation channels are divided into contributions from principal quantum numbers 1 through 4. For dissociative ionization the kinetic energy sharing is calculated using a formally exact expression. These results are compared with approximate expressions, and it is shown that the Born-Oppenheimer result is surprisingly accurate, whereas using Born-Oppenheimer final states to extract the cross sections from the full nonadiabatic wave function produces pathologies near threshold.