The nuclear-charge-expansion method is used in conjunction with a modified screening approximation to predict oscillator strengths, correct through first order in the perturbation, for the 3d-4p and 4p-4d transitions in the sodium isoelectronic sequence. The results are compared with the values recommended by Smith and Wiese.
C. Laughlin, M. N. Lewis, and Z. J. Horak, "Oscillator strengths for the 3d–4p and 4p–4d transitions in sodium-like ions," J. Opt. Soc. Am. 63, 736-738 (1973)