Electron-impact-ionization cross sections for excited states ofBq+(q=0–2) and an investigation intonscaling of ionization cross sections

Abstract

Nonperturbative R-matrix-with-pseudostates (RMPS) and time-dependent close-coupling (TDCC) methods are used to determine electron-impact-ionization cross sections for the excited states of B, B{sup +}, and B{sup 2+}. RMPS calculated cross sections are presented for the 1s{sup 2}2s{sup 2}3l and 1s{sup 2}2s{sup 2}4l configurations of B, the 1s{sup 2}2s3l and 1s{sup 2}2s4l configurations of B{sup +}, and the 1s{sup 2}3l, 1s{sup 2}4l, and 1s{sup 2}5l configurations of B{sup 2+}. It is shown that the TDCC-calculated cross sections for the 1s{sup 2}2s{sup 2}3s configuration of B, the 1s{sup 2}2s3s configuration of B{sup +}, and the 1s{sup 2}3s configuration of B{sup 2+} are in reasonable agreement with the RMPS results. Furthermore, n scaling of these nonperturbative cross sections is investigated and a scheme proposed to allow for the extrapolation of electron-impact-ionization cross sections to higher n shells. Two semiempirical ionization cross-section expressions are fitted to the peak of the highest n-bundled RMPS cross sections for B, B{sup +}, and B{sup 2+}. These are subsequently used for accurate evaluation of the higher n-shell ionization cross sections needed to obtain temperature- and density-dependent generalized collisional-radiative ionization coefficients for the impurity and transport modeling of magnetic fusion plasmas.