Generalized oscillator strength studies for electron-impact 2s ionization of some low- and intermediate-Z atoms

Generalized oscillator strengths (GOS) for ionization of the 2s subshell of several atoms are reported in this paper. The atomic wavefunctions used in the present work have been obtained from a relativistic local density potential method known as the RCE method. The cos has been obtained using the Bom approximation for 2s subshelJ ionization of Be, C, O, Ne, AI, Ar, Fe and Zn. The cos behaviour has been studied both as a function of momentum transfer and energy transfer to understand the Bethe surface properties. Besides the RCE potential, the non-relativistic Hartree-Slater (HS) potential has also been used in a separate calculation for comparison. There is in general reasonably close agreement between the results of the RCE and the HS calculations. The main feature of the GOS for 2s ionization is that in the case of small-Z atoms the GOS at threshold has its maximum at a finite value of K, away from the optical limit (K→0). At the position of the peak, significant contribution from optically forbidden partial wave channels has been observed. The ‘Bethe ridge’ is found to occur when ε ≈ (Ka0)2 at energies above the ionization threshold. At the ionization threshold itself, a ridge on the Bethe surface has been found to occur due to contributions from non-optical channels. © 1994 IOP Publishing Ltd.