X-ray spectroscopy of high n transitions of He- and Ne-like ions in Alcator C-Mod plasmas

The Rydberg series (1s(2)-1snp) up to n = 14 of helium-like argon (Z=18) has been observed from Alcator C-Mod plasmas using a high resolution X-ray spectrometer array. High n satellites to these lines of the form 1s(2)2s-1s2snp and 1s(2)2p-ls2pnp with 3 <= n <= 12 have been recorded. X-ray spectra of 2l-nl' transitions with 3 <= n <= 18 in molybdenum (Z=42) and 3 <= n <= 12 in krypton (Z=36) and niobium (Z=41) from charge states around neon-like have also been measured. Numerous examples of the configuration interaction, which alters the line intensities in some transitions of neon-like ions with nearly degenerate upper levels, have been observed. Accurate wavelengths of all of these transitions (+/-.5 m angstrom) have been determined by comparison to neighboring reference lines from H- and He-like charge states. Line identifications have been made by comparison to ab initio atomic structure calculations, using a fully relativistic, parametric potential code. Measured line intensities have been compared with collisional-radiative modeling that includes the contributions from dielectronic recombination and inner-shell excitation rates, with good agreement.