ELECTRON SCATTERING FROM HYDROGEN ATOMS AND H-LIKE IONS

Abstract

This review, for the Data held at Meudon 1-2 September 1989, provides an update on the last Workshop (at St Catherine's College Oxford, 1987) for data on electron scattering from hydrogen atoms and H-like ions. For hydrogen, the new Energy (IERM) calculation by Scholz et a1 becomes the recommended source of excitation rates for the 1s 2s and Is 2p transitions; for highly charged H-like ions Sampson and Zhang's semiempirical formulae are recommended. 1 UPDATE SUMMARY, 1987-1989 Since the last Atomic Data Workshop held at St Catherine's College Oxford [I] there have been a number of publications describing new work on electron scattering from hydrogen atoms and H-like ions [2-121. We concentrate here primarily on integrated cross sections and excitation rate coefficients, and these are summarised in the following subsections. 1.1 Electron-hydrogen scattering (a) Callaway [2] extended his pseudo-state calculations using the algebraic variational method to calculate 1s 2s and 1s 2p cross sections between the n = 3 and 4 thresholds of hydrogen. (b) Pathak et a1 [3,4] used the R-matrix method to analyse Hresonances to the n-th hydrogenic threshold. (c) Bransden et a1 [5] used the Schwinger variational method to calculate Is 2s cross sections at intermediate energies. (d) Giovanardi and Palla [6] calculated low temperature electron excitation rate coefficients for n = 1,2 to n = 2,3 transitions using cross sections from Callaway et al. (e) Williams 171 provided experimental data on resonances between the n = 2 and n = 3 thresholds. ( f ) Scholz et a1 and Scott et a1 18,9,101 developed an Intermediate Energy R-Matrix method (IERM) to calculate 1s-ls, 1s-2s and 1s-2p cross sections at intermediate energies, and calculated the corresponding effective collision strength, which we reproduce in