Analysis of electron-atom and electron-molecule collisions

Abstract

The relativistic R-matrix method is used to calculate elastic and inelestic cross sections for electrons incident on caesium atoms with energies from 0 to 3 eV. In addition to the total cross sections, results are presented on the differential cross section, σ, and the spin polarization, Py, of the scattered electrons as a function of energy at eight scattering angles (10°, 30°, 50°, 70°, 90°, 110°, 130°, 150°). Also the differential cross section, spin polarization and the left-right asymmetry function, As, are calculated as a function of the scattering angles at a number of chosen values of energies. The calculation reveals a wealth of resonances around 2p1/2 and 2p3/2 thresholds. The resonances are analysed in detail and their role in the scattering process is discussed. The density matrix formalism is used to derive expressions for the Stokes' Parameters to describe the state of the photons emitted in electron-atom collision experiment. Numerical results for the Stokes Parameters of the light emitted in the decay 6p 2p1/2,3/2 -> 6s 2S1/2 in atomic caesium after electron impact excitation are presented and compared with the available measurements. These results show what effects can be expected and may be useful for the planning of future experiments. The angular distribution and the integrated cross sections have been calculated at incident electron energies 20, 25 and 30 eV, in e-N2 scattering. The calculations are based on the use of numerical basis functions in the R-Matrix method, and exchange and polarization effects are included. Also variation of the mixing parameter, between p- and f- partial waves and the individual eigenphases with the internuclear distance are presented. The mixing parameter has shown to be a rapidly varying function of the internuclear distance contradicting the assumption made by Chang (1977).