Electron excitation in helium: including the n=4 levels in an R-matrix calculation
- 28 December 1987
- journal article
- Published by IOP Publishing in Journal of Physics B: Atomic and Molecular Physics
- Vol. 20 (24) , 6631-6640
- https://doi.org/10.1088/0022-3700/20/24/014
Abstract
This is the latest in a sequence of R-matrix calculations on electron-helium scattering in which target states with successively higher principal quantum number are explicitly included in the close-coupling expansion. The 5-state (n<or=2) and 11-state (n<or=3) calculations have already been reported, and now a 19-state (n<or=4) calculation is presented. Such calculations yield accurate excitation cross sections in the collision energy range up to the highest threshold explicitly included; at higher energies, the accuracy of the excitation cross section leaving the atom in a final state of principal quantum number n depends critically on the inclusion of target states with principal quantum number n+1 in the calculation. The inclusion of the n=4 levels of helium in this calculation should therefore yield reliable cross sections and rates for the excitation of the n=3 levels. Collisional excitation rates are calculated which show the extent to which the rates to the n<or=3 levels were overestimated in the previous 11-state calculation.Keywords
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