Triply differential (e,2e) cross sections for He from threshold to 50 eV above

Abstract

Distored wave calculations of the triply differential cross sections for electron-impact ionization of He are presented for electrons sharing ≤50 eV excess energy (E x ) and having the coplanar, θ 12 =π geometry. The results are in good agreement with absolute experimental measurements of T. Rosel et al. [Phys. Rev. A 46 (1992) 2539-2552] and of A. J. Murray, M. B. Woolf, and F. H. Read [J. Phys. B 25 (1992) 3021-3036]. For final state electrons sharing 2 eV excess energy equally, many-body perturbation theory corrections to the author's first order (e,2e) triply differential cross sections [Phys. Rev. A 45 (1992) 4588-4603] are also presented. These results indicate that singlet-triplet interchannel coupling effects in the final state are very significant; that initial state correlations are significant near the perpendicular plane, i.e., θ 1 =θ 2 =π/2; and that the polarization effects we include are insignificant. Finally, comparison of our first order results with the semiclassical quantal theory results of D. S. F. Crothers [J. Phys. B 19 (1986) 463-483] shows excellent agreeement for excess energies E x ≥2 eV and for θ 1 =θ 2 =π/2; for E x <2 eV, the two results diverge as E x →0, indicating that experimental tests of the Wannier-Peterkop-Rau theory of three-body Coulomb breakup should be carried out in this energy region