Abstract

Calculations of the integral and differential cross sections for the electronic excitation of the 21L and 31L states of helium are reported. The multichannel eikonal theory employing a 10-channel basis set is used. The lambda and chi parameters for the 21P and 31P states at 80 eV are also reported. A number of misprints concerning the original multichannel eikonal theory results of Flannery and McCann (1975) have occurred in the literature. These misprints are corrected in the paper. A detailed description of both the theoretical and experimental difficulties involved in the determination of the integral cross sections sigma 11S to 31S and sigma 11S to 31D is provided. In addition, a critique of the assumptions made in previous experimental determinations of the differential cross sections (both composite and magnetic sublevel) for the 21L states of helium is given. A principal conclusion of the paper is that the first Born approximation underestimates experimental data in the intermediate energy region for 1S1D transitions, in contrast to the trend seen in 1S1P transitions. In the paper the importance of indirect mechanisms in the excitation of the 31S and 31D is shown, thereby confirming the early results of Chung and Lin (1968, 1969) and the tentative conclusions of Massey (1969, 1974).

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