Photodissociation and radiative association of HeH+ in the metastable triplet state

Abstract

We investigate the photodissociation of the metastable triplet state of HeH+ as well as its formation through the inverse process, radiative association. In models of astrophysical plasmas, HeH+ is assumed to be present only in the ground state, and the influence of the triplet state has not been explored. It may be formed by radiative association during collisions between a proton and metastable helium, which are present in significant concentrations in nebulae. The triplet state can also be formed by association of He+ and H, although this process is less likely to occur. We compute the cross sections and rate coefficients corresponding to the photodissociation of the triplet state by UV photons from a central star using a wave packet method. We show that the photodissociation cross sections depend strongly on the initial vibrational state and that the effects of excited electronic states and non-adiabatic couplings cannot be neglected. We then calculate the cross section and rate coefficient for the radiative association of HeH+ in the metastable triplet state.

References in corpus (1)

• Molecular fluorine chemistry in the early Universe

Cited by in corpus (4)

• First astrophysical detection of the helium hydride ion (HeH${}^{+}$)
• Detection of vibrational emissions from the helium hydride ion (HeH${}^{+}$) in the planetary nebula NGC 7027
• Determination of photodissociation and radiative association cross sections from the same time-dependent calculation
• Non-thermal photons and direct photodissociation of H2, HD and HeH+ in the chemistry of the primordial Universe