New observations of the spectra of argon X to XV and of isoelectronic emission lines in silicon VII to X, phosphorus X, sulphur IX to XII and chlorine X to XIV

This paper reports the classification of spectral lines of chlorine IX to XIV and of argon X to XV emitted from the plasma formed in a theta pinch. The spectra were recorded photographically using a fast shutter to isolate the period of interest. Additional wavelengths of isoelectronic lines in silicon, phosphorus and sulphur are also presented, these lines were emitted from laser produced plasmas. The transitions identified are 2p n -2p n-1 , 3s, 4s, 3d, 4d, and 2s 2 2p n -2s2p n+1 and 2s2p n -2p n+1 . The wavelengths of the 2s 2 2p n -2s2p n+1 emission lines enable the calculation of ground term intervals in the solar abundant elements silicon, sulphur and argon. The measured interval in argon XIV adds confirmation to the identification of the coronal forbidden line at 4412 AA.