Measurements and calculations of metastable level lifetimes inFeX,FeXI,Fe<

Abstract

Lifetimes of metastable levels in the ground term of Fe ions within the 3s 2 3p k , kϭ1-5, isoelectronic sequences have been measured. These measurements were performed utilizing ions that were selected by mass to charge ratio while transported from an electron cyclotron resonance ion source to a Kingdon ion trap, where they were captured and then confined for periods of up to 2.1 s. During this storage period, selected emission wavelengths of transitions from metastable levels in the visible or near-ultraviolet spectral regions were isolated using interference filters, and the time-dependent fluorescence intensities were measured using a photomultiplier tube. Measurement precisions on the order of 2% were achieved in favorable cases. The measured lifetimes are ͑Fe X, 3s 2 p 5 2 P 1/2)ϭ13.64Ϯ0.25 ms, ͑Fe XI, 3s 2 3p 4 1 D 2)ϭ9.86Ϯ0.22 ms, ͑Fe XII, 3s 2 3p 3 2 P 3/2)ϭ1.85Ϯ0.24 ms, ͑Fe XII, 3s 2 3p 3 2 P 1/2)ϭ4.38Ϯ0.42 ms, ͑Fe XII, 3s 2 3p 3 2 D 3/2)ϭ20.35 Ϯ1.24 ms, ͑Fe XIII, 3s 2 3p 2 1 D 2)ϭ6.93Ϯ0.18 ms, and ͑Fe XIV, 3s 2 3p 2 P 3/2)ϭ17.52Ϯ0.29 ms. These results are compared with existing and with new theoretical calculations, which have estimated uncertainties on the order of 10-25 %.

M1/E2 transition rates in FeXthrough FeXIIImeasured at a heavy-ion storage ring

“…Furthermore, there is the 3s 2 3p3d 3 F o 4 level that is long-lived because there is no level in the lower configurations that it can decay to except by M2 transition (or even higher multipole order). At 9.18 ms (Kohstall et al 1998), the prediction for the lifetime of this level is very close to the lifetime of the 1 D 2 level, and one cannot expect to distinguish the two components from the present data, even as they are statistically much more reliable than those presented by Moehs et al (2000Moehs et al ( , 2001. One question is whether there is any sign of this cascade, and a second is what would need to be done to measure the cascade lifetime.…”

“…Introducing a weak component (less than 10% of the decay curve amplitude) with the predicted lifetime of the cascade level (or other lifetime values up to 10 ms) into a constrained fit, restores the (8.0 ± 0.1) ms result now for the major component, but with an uncertainty that reflects the range of results of various constrained fits and is a factor of five larger than the statistical uncertainty of each of the individual single-component fits. We note that at a higher relative background level, the deviation from a true single-exponential curve would not be recognizable-and this might explain why Moehs et al (2000Moehs et al ( , 2001 do not report such a case from their observations. The Fe 13+ ion (spectrum Fe XIV) has two levels in the 3s 2 3p ground configuration (connected by the astrophysically useful 'green' corona line; the maximum J value is 3/2), various 3s3p 2 levels (among which the 4 P levels with their multi-nanosecond lifetimes are the longest-lived), and the relatively long-lived 3s3p3d 4 F o J levels.…”

“…We note that the Kingdon trap result also deviates from the theoretical predictions (although less than our present preliminary result). We also note that an unspecified background was subtracted from those data before further analysis (Moehs et al 2000(Moehs et al , 2001, which suggests that a similar systematic error of the evaluation may be present in that other experiment. A better signal-to-noise ratio will be needed in order to perform a storage-ring experiment that will settle this case.…”

“…i Bhatia and Kastner (1993). j Moehs et al (2000), Moehs et al (2001). * Tentative result, see text.…”

Orbitrap mass spectrometry: Instrumentation, ion motion and applications

“…It has also been coupled with electron multipliers, Faraday cups, micro-channel plates and photomultiplier tube detectors for spectroscopic interrogation of trapped ions (Church et al, 1999b;Prior & Wang, 1977;Yang & Church, 1991;. In typical experiments, lifetimes of the metastable electronic states of multiply charged ions are measured (Church, Moehs, & Bhatti, 1999a;, 1999Moehs, Church, & Phaneuf, 1998;Moehs et al, 2000;Moehs, Bhatti, & Church, 2001;Smith, Chutjian, & Greenwood, 1999;Smith et al, 2004;Smith, Chutjian, & Lozana, 2005;Yang et al, 1994), providing diagnostic empirical information about the electron density and temperature in astrophysical and laboratory plasmas (Church, 1993;Church et al, 1999b). Submillimeter glass and copper particles (approximately 50-60 mm in diameter) have been confined in the Kingdon trap to study orbital mechanics, with possible implications for understanding the dynamics of asteroids, galaxies, and planetary rings (Biewer et al, 1994;Robertson, 1995;Robertson & Alexander, 1995).…”