Ab initioframe-transformation calculations of direct and indirect dissociative recombination rates ofHeH++e−

Abstract

The $\mathrm{He}{\mathrm{H}}^{+}$ cation undergoes dissociative recombination with a free electron to produce neutral He and H fragments. We present calculations using ab initio quantum defects and Fano's rovibrational frame-transformation technique, employing cation rovibrational wave functions satisfying outgoing wave boundary conditions, to obtain the recombination rate in both the low-energy $(1--300\phantom{\rule{0.3em}{0ex}}\mathrm{meV})$ and high-energy (ca. $0.6\phantom{\rule{0.3em}{0ex}}\text{hartree}$) regions. We obtain very good agreement with experimental results, demonstrating that this relatively simple method is able to reproduce observed rates for both indirect dissociative recombination, driven by rovibrationally autoionizing states in the low-energy region, and direct dissociative recombination, driven by electronically autoionizing Rydberg states attached to higher-energy excited cation channels.