A semiclassical model for polarization forces in collisions of electrons and positrons with helium atoms

Abstract

Abbsbact.A simple semiclassical model is proposed for the calculation of the polarization potential at short range whae the impacting electron penetrates the electron cloud of the target atom. The new method is applied to the scattering of electrons and positrons from He atoms at energies between 0.1 and 50 eV. The model is described in detail and is shown to produce a local effective potential which is computationally wry easy to devise. Calculations for electron scattering are carried out for the elastic integral cross sections and for angular distributions of electrons at several collision energies and compared both with experiments and with more sophisticated calculations. The agreement of the presmt results with experiments is invariably very good. Further test calculations for the positron scattering processes also agree very well with the available experiments and with other theoretid predictions.% Permanent address:

A semiclassical model of polarisation forces in atomic scattering

“…In our earlier calculations for helium atoms [27] we found that the present modelling of polarisation forces gave very good agreement with various existing experiments. The next step in complexity, according to the density renormalization procedure of (32), is to examine the behaviour of computed, integral and differential cross sections for neon.…”

“…To correct for this, various approximate methods for damping the second-order polarisation series have been used over the years in electron-atom and electron-molecule scattering calculations [23,[29][30][31]. Recently we demonstrated that their approach could be successfully applied to the case of electron and positron scattering from the two-electron He atom [27]. In the present we show a simple, global method that provides for a smooth damping of the divergent series with terms up to fourth-order in the perturbation expansion without having to invoke any adjustable parameters for its implementation.…”

“…The coordinate of the bound electron with respect to the target nucleus will be denoted by r b [27]. The coordinate of the bound electron with respect to the target nucleus will be denoted by r b [27].…”

“…In the present work we further test a semiclassical approach recently introduced for electron and positron scattering from helium atoms [27] which describes the short-range behaviour of the response function of the target via an effective model potential. A local, real interaction potential is then constructed to describe the target polarisation in terms of the total electronic density of the bound electrons.…”

The He + ${\rm H}_2^+$H2+ → HeH+ + H reaction: Ab initio studies of the potential energy surface, benchmark time-independent quantum dynamics in an extended energy range and comparison with experiments

“…Parameter free damping functions 43 could also be employed but this requires the calculation of the atomic ground state electronic density and more computational effort is needed. The obtained root-mean-square deviations were 0.0042 and 0.013 meV for the H + 2 and the HeH + ions, respectively, and the largest differences between fitted and calculated energy values were 0.011 and 0.043 meV.…”