The Formula transition array in Fe XX and isoelectronic ions

A detailed analysis of the $$2s^{2} 2p^{2} 3d$$ configuration is presented for ions in the isoelectronic sequence from Si VIII to Fe XX. Slater parameters are adjusted to become consistent with established observational data, and then used to compute energy levels and oscillator strengths of $$2s^{2}2p^{3} - 2s^{2} 2p^{2} 3d$$ transitions. New line identifications are given for this transition array in K XIII, Ca XIV, Sc XV and Ti XVI spectra. Problems arising in the classification of Fe XX lines in the spectra of solar flares and laser-produced plasmas are discussed. The variation of Slater parameters is also discussed for the series of $$2s^{2} 2p^{k-1} 3d$$ configurations (k = 2 to 5) as a whole.