The spectra of Feix to xvi which dominate the XUV spectrum include the 3pn–3p-1 3d transitions studied earlier (Fawcett et al., 1966, 1967, 1968) (Gabriel et al., 1966) and the 3s23pn–3s3pn transitions. A comprehensive classification of spectra from both these configurations is now completed at the Astrophysics Research Unit. The experimental method used to extend the classification of the 3s23pn–3s3pn+1 lines in the period between potassium and vanadium was to compare the spectra of laser produced plasmas which possessed lines belonging to different ionization stages and is described by Fawcett (1970). Too many lines due to low stages of ionization obscured the 3s23pn–3s3pn+1 lines in chromium, manganese, iron, cobalt and nickel in these laser produced spectra for successful analysis. Volatile compounds of these elements were therefore added to the filling gas of a specially designed theta-pinch (Fawcett et al., 1971). Separation of lines of different stages of ionization was accomplished through the application of a microsecond shutter and adjusting the theta-pinch parameters. Radiation from the cooler ends of the plasma was avoided through viewing the theta-pinch from the side.
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