Emission Lines of Fevii–Fexin the Extreme Ultraviolet Region, 60–140 A

Abstract

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.

Low-density laboratory spectra near the He iiλ304 line

“…Moreover, the laboratory permits us to study the spectra of individual elements and have some control over their charge states, whereas observations of the solar corona face the dilemma of a distribution that comprises many elements. We have shown in the past (see, for example, Beiersdorfer et al 1999a;Lepson et al 2002) that laboratory measurements of spectra produced in an electron beam ion trap can be valuable in identifying features either missing from databases or not listed in their natural wavelength positions. Thus our work should help to improve the databases and thus in turn also facilitate the interpretation of solar data.…”

“…On the other hand, the spectra of the few electron ions can be computed well; hence unidentified lines in these cases are likely to belong to ions with more than three electrons, which are less completely known. If one wanted to trace the actual production threshold in order to find out the ionization potential of the ion that produces a given spectral feature, one would have to increment the electron beam energy in much smaller steps than was done here (see Lepson et al 2000Lepson et al , 2002Lepson et al , 2005.…”

Guest Editor’s Notes on the “Atoms” Special Issue on “Perspectives of Atomic Physics with Trapped Highly Charged Ions”

“…By appropriately small beam energy increments, one can track the appearance of new lines and associate them with specific ion charge states, and all that under low-density conditions. This technique has been exercised before especially for iron [24], and it has now been employed by Clementson et al for tungsten, as is described in their contribution to this Special Issue [25]. (Of course, electron beam ion traps are not the only tools used in this research; this journal carries a Special Issue on Atomic Data for Tungsten [26] which describes also very different research methods.…”

Iron emission lines in solar and laboratory plasmas

“…Measurements on EBIT-II utilized similar techniques as those described in earlier measurements of the iron emission [9,10,11,12]. Iron was injected into the trap in the form of iron pentacarbonyl via a gas injector.…”