Classification of Resonance Transitions in Co VIII, Ni IX and Cu X

The 3 s 2 3 p 6 3 d 2 -3 s 2 3 p 5 3 d 3 and 3 s 2 3 p 6 3 d 2 -3 s 2 3 p 5 3 d 4 p , 4 f , 5 f transition arrays of Co VIII are analysed and energy levels established. A few of the strongest Ni IX and Cu X lines from the former array are also identified. Large irregularities along the isoelectronic sequence are found. Theoretical calculations of atomic energy levels and oscillator strengths helped in the identification of spectral lines. The analysis of the Co VIII spectrum will aid the analysis of the isoelectronic Ni IX spectrum. The latter is important because Ni IX emission lines may be present in solar spectra and are radiated from impurities injected into the plasma produced in the nickel-alloy lined vacuum vessels used in Tokamak devices.