Absolute measurements of the energies of resonance lines in heliumlike vanadium on an electron-beam ion trap are reported. The 1s2p 1 P 1 →1s 2 , 1s2p 3 P 2 →1s 2 ͑1s2p 3 P 1 →1s 2 and 1s2p 3 P 0 →1s 2 ͒ blend and 1s2s 3 S 1 →1s 2 transitions are 5205.10 Ϯ 0.14 eV, 5189.12 Ϯ 0.21 eV, 5180.22 Ϯ 0.17 eV, and 5153.82 Ϯ 0.14 eV, respectively. This agrees with recent theoretical calculations and the experimental precision lies at the same level as the current uncertainty in theory ͑0.1 eV͒. These measurements represent a 5.7-8% determination of the QED contribution to the transition energies and are the most precise measurements of heliumlike resonance lines in the Zϭ19-31 range. The measurement of the 1s2s 3 S 1 →1s 2 transition is also sensitive to the 1s2s 3 S 1 QED contribution at the 40% level. The intensity of the strong 1s2p 3 P 1 →1s 2 component of the blend compared to the total blend intensity is 94%Ϯ12%. This is in accord with current theoretical predictions but disagrees with an earlier reported ratio.
We have observed an unusual transition which is predicted to result in visible and near-uv emission from very highly charged titaniumlike ions spanning the entire upper half of the periodic table. Measurements of the wavelengths of the 3d 'D2-D3 transitions in Ba+ and Xe+ are in surprisingly poor agreement with ab initio calculations. This work was carried out in an electron beam ion trap and demonstrates that such a device can be an important tool for visible spectroscopy of highly charged ions. PACS numbers: 32.70.n, 31.25.v, 52.25.b, 52.70.KzAlthough ions having identical numbers of electrons display similar spectral structure, the scale of many atomic properties changes dramatically as the nuclear charge (Z) is increased along an isoelectronic sequence. One example is the rapid decrease in transition wavelengths leading to the characteristic emission of light in the x-ray region of the spectrum for very highly charged ions. It was therefore unusual when Feldman, Indelicato, and Sugar [1] reported calculations predicting a small set of observable visible and near-uv magnetic dipole (Ml) lines for highly charged ions in the titaniumlike isoelectronic sequence. The upper levels of these transitions lie within the ground term, and, therefore, in low density plasmas (~10'3 cm '), where competition from electron
The transition probability for the 3d 4 5 D 2 ← 5 D 3 magnetic-dipole transition in Ti-like Xe ͑Xe 32ϩ ) has been measured using an electron-beam ion trap. The unusually weak dependence of the transition energy on nuclear charge Z, and the fact that the transition wavelength remains in the 320-to 400-nm range for 54ϽZϽ92, makes this transition promising as a plasma diagnostic tool. Our measurement of the transition probability yields 465͑30͒ s Ϫ1 , corresponding to a lifetime of 2.15͑14͒ ms, in good agreement with the theoretical value of 2.4 ms. ͓S1050-2947͑97͒07506-9͔
We have measured the radiative lifetimes for the 2s 2 2p 2 P 3/2 level of Ar 13+ and the 3s 2 3p 2 3 P 2 level of Kr 22+ . These measurements were performed by monitoring the temporal behaviour of their associated radiative decays during magnetic trapping mode in an electron beam ion trap (EBIT). Our lifetime results, 8.7(5) ms for Ar 13+ and 5.7(5) ms for Kr 22+ , are compared with theory.
This paper surveys the ongoing physics experiments at the Electron Beam Ion Trap (EBIT) facility at NIST, with particular attention paid to the underlying physical principles involved. In addition, some new data on the performance of our EBIT are presented, including results related to the determination of the trap width, ion temperature, and number of highly charged ions in the trap.
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