Low-Energy Dissociative Recombination of CH⁺

Modelling the dissociative recombination (DR) of molecular ions becomes complicated when the direct and indirect DR mechanisms compete with each other. This typically occurs in ions with low-energy electronic resonances, e.g., open-shell molecular ions. We present a theoretical approach to model this process that combines three methods: (i) fixed-nuclei electron-ion scattering with the UK R-matrix method, (ii) rovibronic frame transformation with dissociative wave functions obtained with a complex absorbing potential, and (iii) molecular quantum-defect theory. We apply this approach to the CH⁺ ion. Past studies of the DR of CH⁺ have shown that the Rydberg series belonging to the two lowest excited states of the ion, a³Π and A¹Π, and d-type partial waves of the incident electron have a significant impact on the DR cross section. We improve on our recent study of CH⁺, of which the results were only vibronically resolved, by performing a rovibronic frame transformation and present our rotationally resolved results compared against recent experimental data.