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Abstract
X-ray spectra can provide valuable information on the atomic structure and the excitation mechanisms of highly charged ions, and their study is important for x-ray laser and fusion research as well as for the diagnosis of astrophysical and laser-produced plasmas. In the present work, high-resolution spectra of the n = 3 to n = 2 x-ray transitions in neonlike ions have been recorded on the Princeton Large Torus tokamak and are analyzed in detail. The observed spectra fall into the wavelength region 2.00-9.00 A and originate from elements between Z = 34 (selenium) and Z = 63 (europium). A systematic determination of the wavelengths of the neonlike transitions has been made as function of atomic number. The wavelengths of the neonlike lines have been determined with the help of a large number of hydrogenlike and heliumlike reference spectra. The hydrogenlike and heliumlike spectra are also presented. The wavelength measurements are compared to results from advanced computer calculations, and the quantum electrodynamical contributions to the neonlike transition energies have been determined. The spectral line intensities of the neonlike transitions have been measured as a function of electron temperature and atomic number and are compared to theoretical line ratios inferred from electron-impact excitation and radiative decay rates. In addition, the role of inner-shell ionization of sodiumlike ions in the excitation of neonlike ions is investigated. The process is shown to be significant for the excitation of certain neonlike levels, and its rate coefficient has been measured. Time-resolved observations of the neonlike line intensities are used to determine the transport parameters and particle confinement times in tokamak plasmas, and the radial charge-state distribution has been inferred from profile measurements of the sodiumlike, neonlike, and fluorinelike line emission.
