Double-$K$-hole resonances in single photoionization of He-like B${}^{3+}$ ions

Abstract

Within a joint experimental and theoretical research project, single photoionization of He-like B${}^{3+}$ ions was investigated in the energy range from approximately 250 to 1200~eV. With the parent-ion beam in the experiment containing both $1s^2{}^{1}S$ ground-state and $1s2s{}^{3}S$ metastable B${}^{3+}$ ions, double-core-hole resonances could be studied. Two series of hollow resonant states were observed, one populated by $K$-shell double excitation $1s^2{}^{1}S\to 2\ell n{\ell }^{\prime }{}^{1}P$ ($\ell =s,p$; ${\ell }^{\prime }=p,s$; $n=2,3,..,6$) at photon energies up to about 510~eV, the other by $K$-shell single excitation $1s2s{}^{3}S\to 2\ell n{\ell }^{\prime }{}^{3}P$ ($\ell =s,p$; ${\ell }^{\prime }=p,s$; $n=2,3,..,6$) at energies up to about 310~eV. High resolving powers up to approximately 29000 were achieved. The relativistic many-body perturbation theory was employed to determine level-to-level cross sections for $K$-shell excitation with subsequent autoionization. The resonance energies were calculated with inclusion of electron correlation and radiative contributions. The energy uncertainties of the most prominent resonances are estimated to be below $\pm 1$ meV. Convergent close coupling (CCC) calculations provided single-photoionization cross sections ${\sigma }_{34}$ for B${}^{3+}$ including the resonant and non-resonant channels. Apart from the resonances, ${\sigma }_{34}$ is dominated by direct ionization in the investigated energy range. The contribution ${\sigma }_{34}^{\mathrm{dir}}$ of the latter process to ${\sigma }_{34}$ was separately determined by using the random-phase approximation with exchange and relativistic Hartree-Fock calculations which agree very well with previous calculations. Direct ionization of one electron accompanied by excitation of the remaining electron was treated by the CCC theory and found to be a minor contribution to ${\sigma }_{34}$.

arXiv comment27 pages, 19 figures

References in corpus (12)

• QED tests with highly-charged ions
• Absolute cross sections for photoionization of Xe${}^{q+}$ ions (1 $\le$ q $\le$ 5) at the 3d ionization threshold
• Photoionization of metastable heliumlike C4+(1s 2s 3S1) ions: Precision study of intermediate doubly excited states
• QED calculations of energy levels of helium-like ions with $5\le Z\le 30$
• Complex scaled relativistic configuration-interaction study of the $LL$ resonances in helium-like ions: from Boron to Argon
• The photon-ion merged-beams experiment PIPE at PETRAIII - The first five years
• Emergent Behavior in Strongly Correlated Electron Systems
• Analytical expression for the convolution of a Fano line profile with a Gaussian
• A new benchmark of soft X-ray transition energies of Ne, CO${}_2$, and SF${}_6$: paving a pathway towards ppm accuracy
• Radiationless decay spectrum of O 1s double core holes in liquid water
• Single photoeffect on helium-like ions in the non-relativistic region
• Complex-scaled ab initio QED approach to autoionizing states

Cited by in corpus (1)

• An Algorithm for Automated Extraction of Resonance Parameters from the Stabilization Method