Effective collision strengths for fine-structure transitions for the electron impact excitation of N II

Abstract

We present effective collision strengths for the electron impact excitation of singly ionized nitrogen which have been calculated using the R-matrix method. The 23 lowest LS states are included in the expansion of the total wavefunction. These target states arise from the 2s 2 2p 2 ,2 s2p 3 and 2s 2 2p3l(l = s, p, d) configurations, leading to 41 fine structure levels and 820 possible transitions. The fine-structure collision strengths were obtained by transforming to a jj-coupling scheme using the JAJOM program of Saraph and have been determined at a sufficiently fine energy mesh to delineate properly the resonance structure. The effective collision strengths were calculated by averaging the electron collision strengths over a Maxwellian distribution of velocities. Tabulations of the non-zero effective collision strengths are given for electron temperatures (Te )i n the range log10 Te(K) = 2.0−5.5.