Collision strengths for electron impact excitation of inelastic transitions in Ar II

We have calculated collision strengths for electron impact excitation of inelastic transitions in Ar II using the R-matrix method in two independent nine- and 19-state close-coupling approximations. In the nine-state calculation the 3s23p52Po, 3s3p62S, 3p4(3P)4s2P, 3p4)3P)3d2P, 3p4(1)D)4s2D, 3p4(3P)3d2D, 3p4(1S)4s2S, 3p4(1D)3d2S and 3p4(1D)4d2S states are included, while in the 19-state calculation these states plus an additional ten states 3p4(3P)3d2F, 3p4(3)P4p2 Do, 2Po, 2So, 3p4(1D)4p2Po, 2 Do, 2 Fo, 3p4)1D 3d2D, 2P and 3p4(1S)4p2Po are considered. These target states are represented by fairly extensive configuration-interaction wavefunctions which yield excitation energies and oscillator strengths that are generally in good agreement with the most available accurate calculations and the experimental values. Rydberg series of resonances converging to the excited state thresholds are included in the calculation. The effective collision strengths are obtained assuming a Maxwellian distribution of electron energies which are tabulated over the temperature range (0.5-20) x 104K. (author)