The effects of coupling to the target continuum on the electron-impact excitation of Li⁺

BALLANCE, C. P.; BADNELL, N. R.; GRIFFIN, D. C.; LOCH, S. D.; MITNIK, D. M.

JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS

IOP

Lugar: Bristol, London; Año: 2003 vol. 36 p. 235 - 246

0953-4075

We have investigated the effects of coupling to the continuum and high bound states on the electron-impact excitation of He-like Li+ using the R matrix with pseudostates (RMPS) method. Previous studies on this ion have focused on transitions from the ground state to the n = 2 terms. In this work, we have determined collision strengths between all 19 terms through n = 4. We present the results of two RMPS calculations with different numbers of pseudostates in order to study the convergence of the collision strengths with the size of the pseudostate expansion. In addition, we compare the RMPS collision strengths with the results of an R-matrix calculation without pseudostates in order to determine the influence of the continuum coupling as a function of electron energy. As one might expect, coupling to the target continuum has quite large effects on the collision strengths for excitation to the n = 3 and 4 terms at energies above the ionization limit. However, we find that these effects are also significant for excitation to the n = 2 terms and that they persist down to energies just above the excitation thresholds. The experience gained from this work will allow us to pursue similar studies in more complex target systems. Furthermore, the results of our largest RMPS calculation provide the most complete and accurate set of excitation data for this ion, which is of significant importance to research in controlled nuclear fusion.