XUV and soft X-ray laser radiation from nickel-like lanthanide

Atomic structure data and effective collision strengths for 1s(2) 2s(2) 2p(6) 3s(2) 3p(6) 3d(10) a and 54 fine-structure levels contained in the configurations 1s(2) 2s(2) 2p(6) 3s(2) 3p(6) 3d(9) 4l (l = s, p, d, f) for the nickel-like La ion have been investigated. These data are used in the determination of the reduced population for the 55 fine structure levels over a wide range of electron densities (from 10(20) to 10(22)) and at various electron plasma temperatures. The gain coefficients for those transitions with positive population inversion factor are determined and plotted against the electron density.