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Bound-state energies, oscillator strengths and photoionisation cross sections have been calculated for members of the lithium isoelectronic sequence with nuclear charge Z in the range 3 < 2 s 10. Two independent approaches to the problem give virtually the same results. Detailed comparisons with experiment and other theoretical results indicate that the present data are of high accuracy.

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Recent measurements of the photoionization of Na by ejection of a 3s, 2p, or 2s electron give branching ratios, ␤ parameters, and absolute partial cross sections for a number of excitation processes, allowing one to perform the full partition of the total photoabsorption cross section into its components. In parallel, recent developments of the R-matrix code, together with extensive configuration and close-coupling expansions, make it possible to calculate the relevant quantities over the continuum energy range ͑40-140 eV͒ as well as in the resonant energy region corresponding to the excitation of a 2 p or 2s inner-shell electron onto empty optical orbitals. A critical comparison is made of our experimental results with previous and present theoretical calculations. Valuable information is obtained for the ionization energies and relative cross sections. The main limitation in testing the validity of the various theoretical approximations is the lack of accuracy of the experimental photoabsorption cross section measured only to about 25%.

Abstract. This is the third paper in a series giving collision rates for electron excitation of theground state fine-structure transition in aluminiumlike ions. In this paper we give data for the transitions in P iii (17.9 µm), S iv (10.5 µm) and Cl v (6.71 µm). For the P and Cl ions the only existing results are nearly 30 years old and were obtained using a method which does not incorporate resonance effects. For S iv, previous close-coupling calculations do exist but we show that our more elaborate calculation changes the rate coefficients by about 50% at lower temperatures.