EFFECTIVE COLLISION STRENGTHS AMONG FINE-STRUCTURE LEVELS OF CA-XV

Using the R-matrix program, collision strengths Ω for 190 fine-structure transitions among the 1s22s22p2, 1s22s2p3, and 1s22p4 configurations of Ca XV are computed in the energy range of 0-100 Ry. Relativistic effects are included in the computations of Ω through term coupling coefficients. The effective collision strengths T, obtained by averaging Ω over a Maxwellian distribution of electron velocities, are listed for all transitions in the temperature range of 106-107 K. The effects on the calculated Ω and γ values of term coupling and configuration-interaction in the target are examined, and the importance of including relativistic effects is noted, particularly for spin and parity changing transitions at the higher energies and temperatures. A satisfactory agreement is observed, in general, on comparison of the present γ values with those obtained from distorted wave calculations, except for the 3P0 → 1P1°, transition for which the present results are higher by over two orders of magnitude. Therefore, a need is emphasized for another independent calculation to check the discrepancy for this particular transition. However, the line intensity ratios calculated for some of the transitions using the above results show an excellent agreement with the experimentally observed ratios in astrophysical and tokamak plasmas.