OBSERVATION AND MODELING OF HIGH-N IRON L-SHELL LINES FROM INTERMEDIATE ION STAGES

The spectra of highly ionized iron species between 7 and 9 Angstrom ha ve been studied using data obtained at the Princeton Large Torus tokam ak under plasma conditions similar to those present in solar and stell ar flares. The wavelengths of many iron lines are measured with very h igh accuracy (lambda/Delta lambda up to 4 x 10(4)), along with several other lines in species such as He-like Al XII and Mg XI. Theoretical spectra that predict both the wavelength and the intensity of Fe emiss ion lines are compared with the observed spectra and are used to make accurate line identifications. Virtually all the observed iron lines a re found to arise from n = 4, 5, and 6 --> 2 transitions in Fe XXI-XXI V, and many lines are identified for the first time. Several transitio ns are shown to have diagnostic applications, and a detailed analysis of the density sensitivity of Fe XXII lines is presented.