Bound-State Calculation of Scattering Resonance Energies

Abstract

Resonance energies in electron scattering are estimated by calculating bound trial functions which represent electron attachment to the lowest Rydberg state. The trial functions are kept orthonormal to a single-configuration description of the target state and so represent an approximation to the Feshbach procedure. Correlated trial functions are used for He−(2S), Ne−(2P), and Ar−(2P). The resonant-energy predictions are in good agreement with observation. In addition, the correlation energy for the ns2 pairs range from 0.55 to 0.75 eV. These correlation energies are used to correct Hartree–Fock estimates of resonance energies computed for the HF, H2O, and N2 molecules. Energy curves obtained for HF−(2Π) indicate a dissociative attachment process is possible that leads to production of the H− ion. Only single points are calculated for H2O but the B12 resonance state is assigned to a dissociative attachment at 6.5-eV incident electron energy that yields the H− ion. In addition to the attachment to Rydberg excited states, two N2 valence-type Feshbach states are calculated. The results for σgπg2, 4Σg−, and Δg2, when used with correlation energy estimates lead to the conclusion that valence-type Feshbach states are not bound relative to their concomitant neutral excited valence state. Sharp resonances would not then be expected below such neutral states.