We have calculated 1814 energy levels in L S coupling, 33030 oscillator strengths and 859 570 photoionization cross section values for the following fifteen members of the beryllium isoelectronic sequence: Bei, BII, C III, N I V , O V , F V I , NevII, NavIII, MgIx, Alx, S ~X I , SXIII, Arxv, CaxvII andFexxIr1. Photoionization is from 1554 bound states lying below the 2s ionization thresholds. The continua are perturbed by resonances converging onto the 2p, 3s, 3p and 3d states of the residual Li-like ions. We delineat,e the resulting autoionization features by using sufficiently small energy step lengths in regions where the cross sections vary rapidly. Photoexcitation of the core produces large PEC resonances which dominate photoionization of Be I and the less highly ionized ions. We discuss some selected examples drawn from our entire data set and make comparisons with the work of other investigators.

Abstract. The program developed by Burgess for spline fitting and interpolating collision strengths can also be used to do isoelectronic fits. Instead of treating Ω(E) or Υ(T) one inputs an arbitrary quantity A(Z) that is a function of nuclear charge number Z. In this way isoelectronic atomic data can be visualised and compacted in an easy manner which allows for accurate interpolation along a sequence. Four illustrative applications are provided.

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Abstract. We present thermally averaged collision strengths for electron induced transitions in helium from 1s 2 1 S, 1s2s 1,3 S, 1s2p 3 P to higher lying terms 1snl 1,3 L with n ≤ 5. Results are tabulated as functions of temperature in the range 3.75 ≤ log T ≤ 5.75. Cross sections are calculated using the convergent close-coupling (CCC) method.

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