Analysis of discrepancies between quantal and semiclassical calculations of electron impact broadening in plasmas

In this work we analyse the serious discrepancies found between quantal calculations and non-perturbative semiclassical calculations of electron impact broadening in the case of B(2+)2s-2p. We use the Coulomb Bethe (CB) approximation to calculate both electron impact broadening and excitation of 2s-2p for comparison with the other methods. We find good agreement between CB and the non-perturbative semiclassical method for the line width contributions of individual partial waves, except for low L, where strong collision effects enter. We also find good agreement between CB and the R-matrix and Coulomb Born methods for the excitation cross section partial wave contributions, again except for low L. There is disagreement for the high partial wave cross sections between the non-perturbative semiclassical method and all of the quantum methods; this is resolved by applying a symmetrized method, for which we demonstrate excellent agreement with CB. The area in which the semiclassical, Coulomb-Born and R-matrix methods disagree has been reduced to the first three partial waves, and the disagreement must be due to the treatment of strong collisions. (C) 2000 Elsevier Science Ltd. All rights reserved.