Parts-per-million-accurate determination of the K$\alpha$ photoionization resonance of Be-like oxygen with resolution of its ${}^{16}$O-${}^{18}$O isotopic shift

Abstract

We determine with high accuracy the energy of the inner-shell transition $1s^{2}2s^2{}^1{\mathrm{S}}_0\to 1s2s^{2}2p_{3/2}{}^1{\mathrm{P}}_1$ ${}^{16}{\mathrm{O}}_{K\alpha }^{4+}$ at $554.372(3)\mathrm{eV}$ ($\lambda$ = $22.36480(12)~\unicode{x212B}$) as well as its small shift of $2.2\pm 1.3\mathrm{meV}$ ($\Delta \lambda$ = $0.089(52)~\mathrm{m}\unicode{x212B}$) for the ${}^{18}\mathrm{O}$ isotope. This transition blends with a $K_{\alpha }$ line of ${\mathrm{O}}^{5+}$ used in astrophysical diagnostics, potentially affecting its reliability. In contrast to our experimental uncertainty of $\pm 3\mathrm{meV}$, advanced electronic structure predictions for this four-electron system, including quantum electrodynamic (QED) corrections on the order of $100\mathrm{meV}$, still scatter by more than $\pm 250\mathrm{meV}$. Ions generated and stored in an electron beam ion trap were excited at the ELETTRA synchrotron facility with monochromatic soft x rays, with photon energies corrected by an additional spectrometer. Upon resonant excitation of ${\mathrm{O}}^{4+}$ and subsequent autoionization, we separate the photoions of each isotope by a time-of-flight measurement. This way, we resolve soft x-ray isotopic shifts of a few meV, obtain very accurate data on an essential astrophysical ion, and test calculations down to the level of QED contributions.

arXiv comment9 pages, 6 figures, 4 tables, published in Physical Review A

References in corpus (27)

• Observations of the MIssing Baryons in the warm-hot intergalactic medium
• Inner-shell Absorption Lines of Fe~VI-- Fe~XVI: A Many-body Perturbation Theory Approach
• X-ray resonant photoexcitation: line widths and energies of Kα transitions in highly charged Fe ions
• The Heidelberg compact electron beam ion traps
• K-shell Photoabsorption of Oxygen Ions
• The origin of ICM enrichment in the outskirts of present-day galaxy clusters from cosmological hydrodynamical simulations
• Ultrafast outflows disappear in high radiation fields
• Laboratory measurements compellingly support charge-exchange mechanism for the 'dark matter' $\sim$3.5 keV X-ray line
• X-ray/UV campaign on the Mrk 279 outflow: density diagnostics in Active Galactic Nuclei using O V K-shell absorption lines
• Laboratory Measurement and Theoretical Modeling of K-shell X-ray Lines from Inner-shell Excited and Ionized Ions of Oxygen
• Mass- and field-shift isotope parameters for the $2s-2p$ resonance doublet of lithium-like ions
• Relativistic configuration-interaction calculations of energy levels of the $1s^{2}2l$ and $1s2l2l^{\prime }$ states in lithium-like ions: carbon through chlorine
• High-precision measurements of $n=2\to n=1$ transition energies and level widths in He- and Be-like Argon Ions
• Wavelength Measurements of K Transitions of Oxygen, Neon, and Magnesium with X-ray Absorption Lines
• Theoretical energy levels of $1sns$ and $1snp$ states of helium-like ions
• Relativistic configuration-interaction calculation of energy levels of core-excited states in lithium-like ions: argon through krypton
• New Measurement Resolves Key Astrophysical Fe XVII Oscillator Strength Problem
• QED calculations of energy levels of helium-like ions with $5\le Z\le 30$
• X-ray absorption via K-alpha resonance complexes in oxygen ions
• Complex scaled relativistic configuration-interaction study of the $LL$ resonances in helium-like ions: from Boron to Argon
• X-Ray Absorption Analysis of MCG-6-30-15: Discerning Three Kinematic Systems
• An einzel lens with a diagonal-slit central electrode to combine steering and focusing of a low energy ion beam
• Discovery of Galactic OIV and OV X-ray absorption due to transition temperature gas in the PKS 2155-304 spectrum
• High-Precision Determination of Oxygen-K$\alpha$ Transition Energy Excludes Incongruent Motion of Interstellar Oxygen
• High-Precision Transition Energy Measurements of Neon-like Fe XVII Ions
• Natural-linewidth measurements of the 3C and 3D soft-x-ray transitions in Ni XIX
• Complex-scaled ab initio QED approach to autoionizing states