Threshold peaks in electron scattering by HF and HCl

The R‐matrix method is used to calculate low energy ab‐initio elastic scattering and vibrational excitation cross sections for electrons scattered by HF and HCl. In the case of HCl, dissociative attachment cross sections are also determined. Nuclear vibration and dissociative attachment is included using a non‐adiabatic approach. Sharp peaks are found in the vibrational excitation cross section close to each vibrational threshold for both molecules in qualitative agreement with experiment. These peaks correspond to poles in the S‐matrix and can be interpreted as nuclear‐excited Feshback resonances.