Threshold photoelectron source for the study of low-energy electron scattering: Total cross section for electron scattering from krypton in the energy range from 14 meV to 20 eV

Abstract

An experimental technique for the measurement of the total cross section for electron scattering from atoms and molecules at high resolution is described. The total cross sections for electron scattering from Kr in the energy range from 14 meV to 20 eV obtained with the technique are also reported. The present technique employs a combination of the penetrating field technique and the threshold photoionization of rare-gas atoms using synchrotron radiation as an electron source in order to produce a high-resolution electron beam at very low energy. The characteristics of the electron sources were determined by measuring the ionizing photon energy dependence of photoelectron yield. Absolute total cross sections for electron scattering are obtained by the attenuation method. The measured absolute values of the total cross sections for electron scattering from Kr agree with those obtained by other groups down to 175 meV, above which several experimental works have been reported. Below 175 meV, the present results generally agree with theoretical cross sections down to 14 meV. The resonant structures in the total cross sections due to Kr${}^{\ensuremath{-}}$ ($4{p}^{5}5{s}^{2 2}{P}_{3/2}$) and the Kr${}^{\ensuremath{-}}$ ($4{p}^{5}5{s}^{2 2}{P}_{1/2}$) Feshbach resonances are also reported. The resolution of the present setup has been estimated from a fit of the measured profile of the Kr${}^{\ensuremath{-}}$ ($4{p}^{5}5{s}^{2 2}{P}_{3/2}$) resonance by the theoretical curve obtained from the resonant scattering theory.