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M-shell spectra of W ions have been produced at the Lawrence Livermore National Laboratory EBIT-II electron beam ion trap-II at different energies of the electron beam. A survey has been performed at 2.4, 2.8, and 3.6 keV, and for steps in energy of 100 eV over the 3.9–4.6 keV energy range. The analysis of 11 W spectra has shown the presence of a wide variety of ionization stages from Se-like to Cr-like W; the appearances of these ionization stages correlate well with the energy of their production. The present paper focuses on the identification of 63 experimental features of W ions in a spectral region from 5 to 6 Å (1 Å = 10–10 m) using calculations with inclusion of all ionization stages matching this spectral region. The majority of lines in all spectra have been identified and assigned to the 4f → 3d and 4d → 3p transitions. This is the first work that lists a comprehensive identification of so many resolved spectral features of X-ray M-shell transitions in W ions recorded in such detail in the laboratory. PACS Nos.: 52.58.Lq,32.30.Rj,52.70.La

We report laboratory studies of the role played by multiple-electron capture (MEC) in solar wind-induced cometary X-ray emission. Collisions of Ne 10ϩ with He, Ne, Ar, CO, and CO 2 have been investigated by means of the traditional noncoincident-singles X-ray spectroscopy in addition to the triple-coincidence measurements of X-rays, scattered projectile, and target recoil ions for the atomic targets. The coincidence measurements enable one to reduce the singles X-ray spectra into partial spectra originating in single-electron capture (SEC) and MEC collisions. The measurements provide unequivocal evidence of the significant role played by MEC and strongly suggest that models based solely on SEC are bound to yield erroneous conclusions on the solar wind composition and velocities and on cometary atmospheres. The experimental relative importance of MEC collisions is compared with the molecular classical-over-the-barrier model, the classical trajectory Monte Carlo technique, and the multichannel Landau-Zener method, calculations that can qualitatively reproduce the experimental trends.

Transition probabilities of three magnetic dipole (M1) transitions in multiply charged ions of Ar have been measured using the Livermore electron-beam ion trap. Two of the transitions are in the ground conÐgurations of Ar XIV (B-like) and Ar IX (F-like), and are associated with the coronal lines at 4412.4 and 5533.4respectively. The third is in the excited 2s2p conÐguration of Be-like Ar XV and produces A , the coronal line at 5943.73Our results for the three atomic level lifetimes are 9.32^0.12 ms for the A . Ar X 2s22p5 level, 9.70^0.15 ms for the Ar XIV 2s22p level, and 15.0^0.8 ms for the Ar XVlevel. These results di †er signiÐcantly from earlier measurements and are the most accurate 3P 2 o ones to date.