Computing more accurate scattering cross-sections for H₂⁺+e^- in the gerade symmetry

An accurate calculation of dissociative recombination and rovibrational excitation cross sections for electron impact with diatomics such as H₂⁺ has been a long-standing problem of AMO physics. Successfull approaches typically employ MQDT techniques such as rovibrational frame transformation with various additional approximations (such as neglecting the energy dependence of asymptotic quantities). There are, however, such cases of diatomics (e.g. H₂⁺ in the gerade symmetry), where the presence of multiple coupled target states makes these approximations undesirable and an accurate treatment is much harder to set up.

We present our ongoing effort to increase the accuracy and reliability of MQDT methods by tackling the case of gerade H₂⁺ electron scattering with multiple enhanced approaches such as an ab-initio R-matrix calculation (Phys. Rev. A 98, 062706 (2018)), an energy-dependent rovibrational frame transformation employing ECS states (Phys. Rev. A 101, 012709 (2020)) and a reformulated version of the "Unified quantum-defect theory of molecular ionization and dissociation" treatment of Ross and Jungen (Phys. Rev. A 55, R2503 (1997)). We set up a two dimensional model potential for the eletron-molecule interaction and study the efficacy and validity of these methods.