Extreme ultraviolet spectra of highly charged Xe ions
TL;DR: In this article, the SuperEBIT electron-beam ion trap and a flat-field spectrometer were used to observe extreme ultraviolet spectra of highly charged ions of Xe and measured the wavelengths of prominent lines from Li-, Be-, B-, Na-, and Mg-like ions.
Abstract: Using the SuperEBIT electron-beam ion trap and a flat-field spectrometer, we observed extreme ultraviolet spectra of highly charged ions of Xe and measured the wavelengths of prominent lines from Li-, Be-, B-, Na-, and Mg-like ions. Our results for Li- and Na-like ions are as precise as the best available elsewhere. The results for Be-, B-, and Mg-like ions are much more precise than available data or extend those available from lower-$Z$ ions and reveal significant shortcomings of the various theoretical predictions.
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TL;DR: The current status of bound state quantum electrodynamics calculations of transition energies for few-electron ions is reviewed in this paper, where the impact of the nuclear size correction on the quality of QED tests as a function of the atomic number is discussed.
Abstract: The current status of bound state quantum electrodynamics calculations of transition energies for few-electron ions is reviewed. Evaluation of one and two body QED correction is presented, as well as methods to evaluate many-body effects that cannot beevaluated with present-day QED calculations. Experimental methods, their evolution over time, as well as progress in accuracy are presented. A detailed, quantitative, comparison between theory and experiment is presented for transition energies in few-electron ions. In particular the impact of the nuclear size correction on the quality of QED tests as a function of the atomic number is discussed.The cases of hyperfine transition energies and of bound-electron Land{e} $g$-factor are also considered.
63 citations
TL;DR: In this article, a flat field, extreme ultraviolet spectrometer built specifically for use with low power light sources that operate under ultrahigh vacuum conditions is reported, whose spectral range extends from 4 nm to 40 nm.
Abstract: A custom, flat field, extreme ultraviolet spectrometer built specifically for use with low power light sources that operate under ultrahigh vacuum conditions is reported. The spectral range of the spectrometer extends from 4 nm to 40 nm. The instrument optimizes the light gathering power and signal-to-noise ratio while achieving good resolution. A detailed description of the spectrometer and design considerations are presented, as well as a procedure that could be used to obtain a synthetic wavelength calibration with the aid of only a single known spectral feature. This synthetic wavelength calibration is compared to a standard wavelength calibration obtained from previously reported spectral lines of Xe, Ar, and Ne ions recorded with this spectrometer.
47 citations
TL;DR: In this paper, high-Z lithium-like ions are used to test two-loop quantum electrodynamics at a level similar to that achieved with atomic hydrogen, but the uncertainties associated with the proton charge radius and the finite size of highZ nuclei, respectively, are discussed.
Abstract: Measurements of high-Z hydrogen-like ions have not yet been able to compete with the ultra-high precise test of quantum electrodynamics (QED) carried out using atomic hydrogen. However, recent advances in theory and experiment have enabled measurements involving high-Z lithium-like ions to test two-loop QED at a level similar to that achieved with atomic hydrogen. Tests of two-loop QED are limited in both cases by the uncertainties in the finite nuclear size, i.e. the uncertainties associated with the proton charge radius and the finite size of high-Z nuclei, respectively. Future experiments employing high-Z ions are described that might go beyond the present limitations. Measurements of the hyperfine splitting in highly charged ions cannot readily be described by theory, in part because of poor understanding of the finite nuclear magnetization radius. The discrepancy between measurements and theory leaves open the possibility of new physics not yet addressed by our current understanding of atomic–nuclear interactions.
43 citations
TL;DR: In this paper, an electron beam ion trap and a flat field spectrometer were used to measure the extreme ultraviolet spectra of xenon ions in the 4.5 to 20 GHz wavelength region.
Abstract: Extreme-ultraviolet spectra of xenon ions have been recorded in the 4.5 to $20\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$ wavelength region using an electron beam ion trap and a flat field spectrometer. The electron beam energy was varied from $180\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ to $8\phantom{\rule{0.3em}{0ex}}\mathrm{keV}$ and radiation from charge states ${\mathrm{Xe}}^{6+}$ to ${\mathrm{Xe}}^{43+}$ was observed. Our measured wavelengths were compared to atomic structure calculations using the Cowan suite of codes. We have measured seventeen previously unreported features corresponding to transitions in ${\mathrm{Xe}}^{35+}$ through to ${\mathrm{Xe}}^{41+}$ with estimated wavelength uncertainties of $\ifmmode\pm\else\textpm\fi{}0.003\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$. It was found that for the case of continuous injection of neutral xenon gas a wide range of charge states were always present in the trap but this charge state distribution was greatly narrowed, towards higher charge states, if a sufficiently low gas injection pressure was employed. The energy dependence of spectral lines arising from ${\mathrm{Xe}}^{42+}$ and ${\mathrm{Xe}}^{43+}$ revealed enhancement of the total ionization cross sections, due to excitation-autoionization of $n=2$ electrons to $n=3$ levels, in the ${\mathrm{Xe}}^{41+}$ and ${\mathrm{Xe}}^{42+}$ charge states.
41 citations
TL;DR: The interpretation of atomic observations by theory and the testing of computational predictions by experiment are interactive processes as mentioned in this paper, and it is necessary to gain experience with "the other side" before claims of achievement can be validated and judged.
Abstract: The interpretation of atomic observations by theory and the testing of computational predictions by experiment are interactive processes. It is necessary to gain experience with “the other side” before claims of achievement can be validated and judged. The discussion covers some general problems in the field as well as many specific examples, mostly organized by isoelectronic sequence, of what level of accuracy recently has been reached or which atomic structure or level lifetime problem needs more attention.
30 citations
Cites background or methods or result from "Extreme ultraviolet spectra of high..."
...Experimental data at high Z are sparse [102]....
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...two intercombination transitions are close to each other and can be obtained from the same spectrum (see [102])....
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...However, for a decisive test, the experiment could be made even cleaner than before: a collaboration of Heidelberg and Livermore EBIT experts and their associates prepared a sample of Fe16+ ground state ions (with some lower, but no higher charge state ions in the trap) in the usual way (by electron beam ionization and excitation)....
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...This demand has been met best in the range from B (Z = 5) to S (Z = 16), with measurements at the TSR heavy-ion storage ring and at the Livermore EBIT [87–92]....
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...At the Livermore EBIT, the 4s1/2 - 4p3/2 resonance line has been followed along the isoelectronic sequence up to Z = 92, and the data [103,252] have been compared to the veteran computations....
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References
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TL;DR: Theoretical energy levels and energy-level separations for n = 1 and n = 2 states of hydrogen-like atoms with nuclear charge numbers in the range 1 ⩽ Z⩽ 110 are tabulated in this paper.
501 citations
TL;DR: The unified method described previously for combining high-precision nonrelativistic variational calculations with relativistic and quantum electrodynamic corrections is applied to the 1s2 1S0, 1s 2 S 0, 1 s 2 S 1S 0 as discussed by the authors.
Abstract: The unified method described previously for combining high-precision nonrelativistic variational calculations with relativistic and quantum electrodynamic corrections is applied to the 1s2 1S0, 1s2...
357 citations
TL;DR: Theoretical wavelengths, oscillator strengths, line strengths, and transition probabilities for the E1, M1, and E2 transitions among states with 2sn2pm configurations are presented for ions isoelectronic to the first-row atoms (Li through F) in this paper.
324 citations
TL;DR: Ionization potentials for all the elements up to Z = 103 for all states of ionization have been calculated in this paper, based on a simple spherical shell solution for neutral atoms.
277 citations
TL;DR: A highly efficient visible-UV monochromator and a coma-type aberration-reduced Seya-Namioka monochromaator have been designed and fabricated using mechanically ruled aberration -corrected concave gratings.
Abstract: Aberration-corrected concave gratings with curved and variable spacing grooves are ruled with a numerically controlled ruling engine. In the design of aberration-corrected concave gratings, mechanical methods allow more freedom to choose the amount of space variation than do holographic methods. A highly efficient visible–UV monochromator and a coma-type aberration-reduced Seya-Namioka monochromator have been designed and fabricated using mechanically ruled aberration-corrected concave gratings. The gratings can be used with VUV monochromators and spectrographs with improved image focusing properties.
253 citations