Theoretical Studies of Dissociative Recombination of Electrons with SH$^+$ Ions

We are investigating the dissociative recombination (DR) of electrons with the molecular ion SH$^+$, i.e. $e^- + \mathrm{SH}^+ \rightarrow \mathrm{S + H}$. SH$^+$ is found in the interstellar medium, and understanding its loss through DR will lead to more accurate astrophysical models. Recently we addressed the $^2\Pi$ potential energy curves (PECs) of SH as a DR pathway\footnote{Kashinski \emph{et al.}, J.\,Chem.\,Phys. \textbf{146}, 204109\,(2017)}. We have extended this work to investigate alternate DR pathways. Early results suggest that direct-mechanism DR through a $^4\Pi$ pathway may resolve the low-energy ($< 10\,\mathrm{meV}$) discrepancy between experimentally determined rate coefficients and those determined through the indirect mechanism DR $^2\Pi$ pathway. PECs are obtained by performing large active space multi-reference configuration interaction (MRCI) electronic structure calculations for several values of SH separation. Rydberg-valence coupling has proven to be important. The block diagonalization method is used to disentangle interacting states forming a diabatic representation of the PECs. The status of this ongoing work will be presented at the conference.