Abstract
Near-threshold ionization of He has beenstudied by using a uniform semiclassical wavefunction for thetwo outgoing electrons in the final channel. The quantum mechanical transition amplitude for the direct and exchangescattering derived earlier by using the Kohn variationalprinciple has been used to calculate the triple differentialcross sections. Contributions from singlets and triplets arecritically examined near the threshold for coplanar asymmetricgeometry with equal energy sharing by the two outgoingelectrons. It is found that in general the triplet contributionis much smaller compared to its singlet counterpart. However, atunequal scattering angles such as θ1 = 60°,θ2 = 120° the smaller peaks in the triplet contributionenhance both primary and secondary TDCS peaks. Significantimprovements of the primary peak in the TDCS are obtained forthe singlet results both in symmetric and asymmetric geometryindicating the need to treat the classical action variableswithout any approximation. Convergence of these cross sectionsare also achieved against the higher partial waves. Presentresults are compared with absolute and relative measurements ofRösel et al (1992Phys. Rev. A 46 2539) and Selles et al(1987 J. Phys. B. At. Mol. Phys. 20 5195) respectively.
Published Version
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