ATOMIC DATA AND SPECTRAL-LINE INTENSITIES FOR FE-XI

Electron impact collision strengths and spontaneous radiative decay ra tes are calculated for Fe XI. The data pertain to the 48 levels of the configurations 3s(2)3p(4), 3s3p(5), 3s(2)3p(3)3d, and 3p(6). Collisio n strengths are calculated at three incident electron energies, 8.0, 1 6.0, and 24.0 Ry. Relative spectral line intensities are calculated fo r all astrophysically important transitions. These are obtained by com puting the excitation rate coefficients, i.e., the collision strengths integrated over a Maxwellian electron distribution, and then solving the equations of detailed balance for the populations of the 48 energy levels, assuming a collisional excitation model and an electron tempe rature of 1.3 x 10(6) K. This temperature is typical for Fe XI when fo rmed in equilibrium by collisional ionization and recombination. Using the excitation rate coefficients and the radiative decay rates, level populations are computed for several electron densities and are given in this paper. We also investigate the effects of proton excitation a nd solar radiative excitation on the level populations and line intens ities. Finally, the calculated relative line intensities are compared with experimental solar intensities where available. (C) 1996 Academic Press, Inc.