Rovibrationally-Resolved Photodissociaton of SH$^+$

Abstract

Photodissociation cross sections for the SH$^+$ radical are computed from all rovibrational (RV) levels of the ground electronic state X$~^3\Sigma^-$ for wavelengths from threshold to 500~\AA. The five electronic transitions, $2~ ^3\Sigma^- \leftarrow$ X$~^3\Sigma^-$, $3~ ^3\Sigma^- \leftarrow$ X$~^3\Sigma^-$, $A~ ^3\Pi \leftarrow$ X$~^3\Sigma^-$, $2~ ^3\Pi \leftarrow$ X$~^3\Sigma^-$, and $3~ ^3\Pi \leftarrow$ X$~^3\Sigma^-$, are treated with a fully quantum-mechanical two-state model, {i.e. no non-adiabatic coupling between excited states was included in our work.}. The photodissociation calculations incorporate adiabatic potentials and transition dipole moment functions computed in the multireference configuration interaction approach along with the Davidson correction (MRCI+Q), but adjusted to match available experimental molecular data and asymptotic atomic limits. Local thermodynamic equilibrium (LTE) photodissociation cross sections were computed which assume a Boltzmann distribution of RV levels in the X$~^3\Sigma^-$ molecular state of the SH$^+$ cation. The LTE cross sections are presented for temperatures in the range 1000-10,000~K. Applications of the current photodissociation cross sections to interstellar gas, photon-dominated regions, and stellar atmospheres are briefly discussed.