AN ABINITIO STUDY OF RESONANT LOW-ENERGY ELECTRON-SCATTERING BY HCL

A recently proposed ab initio method for calculation of shape resonances, which is based on the Feshbach formalism, is applied to low-energy electron scattering of the HCl molecule. A metastable 2-SIGMA+ state of the HCl- anion is assumed to be responsible for the structures, which have been found experimentally in the excitation cross section. In our approach resonances are described by a metastable anion, the so-called discrete component. This anion is obtained by a stabilization procedure invoking an increase of the electron-nuclei interaction. The use of a configuration interaction procedure for the calculation of the resonant state provides for a description of correlation and polarization effects between target and projectile. The construction of the metastable 2-SIGMA+ state is discussed in detail as well as the influence of the stabilization on the wavefunction of the molecule and the anion. Scattering calculations are carried out at the fixed-nuclei level with the thus-defined discrete component. The energy-dependent decay width and the level shift as well as the fixed-nuclei cross section are presented. The latter exhibits not only a pronounced shape resonance but also a peak at the threshold for elastic scattering.