ISOELECTRONIC BEHAVIOR OF RESONANT AND INTERCOMBINATION LINES IN MGI-LIKE IONS

The observed intensity ratio of the 3s(2) S-1(0) - 3s3p P-1(1) to the 3s(2 1)S(0) - 3s3p P-3(1) transitions in MgI-like ions has always pres ented those who model plasma spectra with a challenge; the observed in tensity of the intercombination line is always several times greater t han what simple models predict. We offer a model that takes into accou nt the contribution to the MgI-like emission features from autoionizin g levels of the adjacent All-like charge state. Models in the present work give good agreement with the observed resonant/intercombination ( R/I) emission ratio only when a departure from ionization equilibrium is assumed. We also identify, for the first time, intercombination lin es of the form 3s3p P-1(1) - 3p(2) P-3(2) in several elements relevant to both astrophysical and magnetically-confine fusion plasmas.