As part of a larger project to complete a comprehensive catalog of astrophysically relevant emission lines in support of new-generation X-ray observatories using the Lawrence Livermore electron beam ion traps EBIT-I and EBIT-II, we present observations of argon lines in the extreme-ultraviolet region. Our database includes wavelength measurements with standard errors, relative intensities, and line assignments for Ar ixAr xvi between 20 and 50 Å . The experimental data are complemented with a full set of calculations using the Hebrew University Lawrence Livermore Atomic Code (HULLAC). Despite differences in calculated and measured wavelengths, we find the calculated lines to be of great utility in analyzing our laboratory spectra. The calculated line intensities are generally sufficient to identify the strongest transitions in each charge state. We note, however, an underestimation by theory of the strength of the 3s ! 2p lines relative to the 3d ! 2p lines in Ar ix, Ar x, and Ar xi. The laboratory data are compared with Chandra observations of Procyon, resulting in the identification of an Ar ix line that was previously thought to be from S ix.

We report on emission spectra of iron in the extreme ultraviolet recorded at an electron density of $5 Â 10 11 cm À3 at the Lawrence Livermore electron beam ion trap EBIT-II. We present a summary of observed emission lines, including wavelengths and emission intensities. We also illustrate our technique for isolating pure charge states of the desired ion and present spectra of pure Fe vii-Fe x. Our measurements add a large number of newly identified lines to existing line lists in the extreme-ultraviolet region, 60-140 Å . While many of these lines are quite weak, they add up to a significant flux that can seriously affect interpretations of global fitting models, especially when applied to stars with material at the appropriate temperatures, such as Procyon, Cen, and the Sun.

We present high-resolution crystal spectroscopy measurements of the n = 3 → n = 2 L-shell x-ray transitions of neonlike W 64+ , which include seven electric dipole allowed transitions, two electric quadrupole transitions, and one magnetic quadrupole transition. The resulting wavelength data are compared to recent calculational results, allowing us to clearly distinguish between different theoretical approaches, which need to take into account not only substantial electron correlations effects but also radiative contributions, which in case of the transition from upper level (1s 2 2s 1/2 2p 6 3p 3/2) J=1 to the closed-shell neonlike ground state exceeds 20 eV. Best agreement is found with calculations utilizing the relativistic multi-reference Møller-Plesset approach. In addition to the emission from W 64+ , we have observed several innershell collisional satellite lines associated with oxygenlike W 66+ , fluorinelike W 65+ , sodiumlike W 63+ , and magnesiumlike W 62+ , which provide benchmarks for future calculations as well as for recent calculations using the relativistic many-body perturbation theory. The present measurements also provide accurate rest wavelengths for establishing the instrumental dispersion needed for future measurements of the core plasma motion in the ITER tokamak and show that the candidate W 64+ line for such measurements remains well isolated from neighboring collisional satellite lines even when broadened by the expected, high temperatures in this device.

Using the SuperEBIT electron-beam ion trap and a flat-field spectrometer, we observed extreme ultraviolet spectra of highly charged ions of Xe and measured the wavelengths of prominent lines from Li-, Be-, B-, Na-, and Mg-like ions. Our results for Li-and Na-like ions are as precise as the best available elsewhere. The results for Be-, B-, and Mg-like ions are much more precise than available data or extend those available from lower-Z ions and reveal significant shortcomings of the various theoretical predictions.

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