Generalized oscillator strengths for the resonance transitions in alkaline-earth atoms

Abstract

The generalized oscillator strengths (GOS), which are essential factors in the Born cross sections, have been calculated for the lowest P1 transitions in Mg, Ca, Sr, and Ba from the multiconfiguration Hartree-Fock wave functions with two or three configurations each in the ground and the excited states. The optical limits (f values) of the GOS agree with experimental values to within 12%. Theoretical data on zero minima and subsequent maxima in the GOS are presented. Our data show that the resonance transition in Ba is the most favorable one for experimental study of the extrema. Since the Born cross sections vanish at the minima, the experimental study of the minima would reveal valuable information on the validity of the first Born approximation, as well as on the magnitudes of higher-order effects not included in the theory. Data for the integrated Born cross sections are presented also. Recent electron-impact data on the resonance transition of Ca agree with the integrated cross section to within 5% for incident energies of 250 eV and higher. Our data show that the relativistic effects in the cross section for Ba are minor compared to the correlation effect between the two valence electrons. © 1973 The American Physical Society.