Relative intensities of 2s22pk-2s2

B. C. Stratton

¹

,

H. W. Moos

²

,

S. Suckewer

³

et al.

Abstract

Measured relative intensities of a number of allowed 2s 2p -2s2p +' transitions (60 -200 A) in the F I -to B I -like ions of titanium, chromium, iron, nickel, and germanium are compared with values from level-population calculations. The measurements are from Princeton Large Torus (PLT) tokamak plasmas with electron densities of -2.5)&10' cm . For titanium and chromium, data from plasmas with densities of -5&10' cm are also presented; a number of densitydependent line-intensity ratios are found. The spectra were obtained with use of a grazing-incidence time-resolving spectrograph which was radiometrically calibrated with use of synchrotron radiation from the National Bureau of Standards Synchrotron Ultraviolet Radiation Facility (SURF II). The measured relative intensities are therefore reliable. For the majority of the observed lines, agreement between the measured and calculated relative intensities is within 30%%uo, the estimated accuracy of the measurements; significant discrepancies are found in the titanium ions at the low density. The discrepancies, some of which are due to blends, are discussed. Thus, the level-population calculations may be used with some confidence for spectroscopic plasma diagnostics. In the C I -like ions, there is some evidence that calculations which include proton-collisional excitation and deexcitation between the levels of the ground configuration are in better agreement with the measurements than those that do not, indicating that proton collisions should be included in the calculations for these ions.

X-ray and extreme-ultraviolet emission from the coronae of Capella

“…The uncertainties for the Linsky et al and Mathioudakis (1999) observations are those quoted by these authors, and the Dupree et al (1993) uncertainty set equal to the average of the Linsky et al uncertainties. We also include a solar‐flare value from the OSO‐5 spacecraft (Kastner, Neupert & Swartz 1974; Mason et al 1984: uncertainty estimated from the calibration necessary in this measurement) and values from the Princeton Large Torus (PLT) tokamak with electron densities measured by a microwave interferometer (Stratton, Moos & Finkenthal 1984; Stratton et al 1985). With the uncertainties on the Capella and solar points, it would seem that none of the points are much above the low‐density limit, i.e.…”

Spectral properties of a few F-like ions

“…As an example, Foster et al (1994) have determined cross-sections and rate coefficients for the 2s 2 2p 5 2 P 3/2 → 2s 2 2p 5 2 P 1/2 transition in the Ti XIV, Ni XX, Zn XXII, and Mo XXXIV ions by considering the proton, deuteron, trition and α particles impact by using the calculated radiative decay rates in the closed-coupling method. Also, observations of the spectral lines due to both the allowed and forbidden transitions of the Fe XVIII and Ni XX ions are reported (Suckewer & Hinnov 1979;Doyle 1983;Stratton et al 1985;Acton et al 1985;Wang et al 1988). Precise values of the transition probabilities for the highly charged ions that are due to the forbidden channels are of particular interest to physicists for diagnosing the low-density magnetically confined high temperature laboratory plasma generated in tokamak (Currell 2003).…”

Laboratory observation and modeling of extreme ultraviolet spectra of highly ionized calcium

“…Proton collisions can change populations of closely spaced fine structure levels, such as Ca XVI − Ca XIII ground levels. Stratton et al (1985) demonstrated that for the Ti, Cr, Fe and Ni ions this effect is weak, with the exception of carbon-like ions. Since electron impact excitation is the main source of excited level population at the typical tokamak temperature and density, the accuracy of the electron excitation rate coefficients is critical for calculating accurate spectral line intensities.…”