Reflection-free complex absorbing potential for electronic structure calculations: Feshbach type autoionization resonance of Helium

This work represents the first successful application of reflection-free complex absorbing potential (RF-CAP) method to the study of resonances in many-electron systems. The present work introduces a systematic way for implementing RF-CAP for the electronic structure calculations using Gaussian basis sets. The method is applied to study the lowest 1S Feshbach type autoionization resonance of He. It is shown that in order to be able to introduce the RF-CAP close to the nucleus, where the electron-nucleus Coulomb attraction force is not negligible, the RF-CAP should be supplemented by a weak static field.