Two-electron One-photon Transition Research Articles

QED calculation of two-electron one-photon transition probabilities in He-like ions

We consider theoretically the process of two-electron one-photon (TEOP) transitions to the ground state with the emission of a single ${K}_{\ensuremath{\alpha}\ensuremath{\alpha}}$ photon in a He-like sequence of atomic ions: from boron to uranium. The corresponding transition probabilities and transition energies are calculated within the QED theory. The calculations of the transition probabilities are performed in various gauges. The intensity ratios between the TEOP transitions and the other major transitions are presented.

Spectator electron effects on the two-electron one-photon radiative transition process of double K hole state of Xe[formula omitted] ion([formula omitted

The double electron E1 transition energies, probabilities, and oscillator strengths between the 2s2pn and 1s22pn−1(1≤n≤6) configurations of Xeq+(47≤q≤52) ions with different spectator electrons have been calculated based on the multi-configuration Dirac-Hartree-Fock method. A reasonable electron correlation model is constructed with the aid of the active space method. The finite mass of nuclear, Breit interaction and QED effects have also been included. The calculated results are in good agreement with the available data. The theoretical spectra of different spectator electrons of the double K hole state have been predicted. The spectator electron effects on the transition spectra have been analyzed in detail. The present results will be helpful for analyzing the high energy X-ray spectrum observed from the interaction between high energy highly charged ions and the surface.

Effects of electron correlation and the Breit interaction on one- and two-electron one-photon transitions in double K hole states of He-like ions (10 ≤ Z ≤ 47)**Project supported by the National Natural Science Foundation of China (Grant Nos. U1832126 and 11874051) and the National Key Research and Development Program of China (Grant No. 2017YFA0402300).

The x-ray energies and transition rates associated with single and double electron radiative transitions from the double K hole state 2s2p to the 1s2s and 1s2 configurations of 11 selected He-like ions (10 ≤ Z ≤ 47) are calculated using the fully relativistic multi-configuration Dirac–Fock method (MCDF). An appropriate electron correlation model is constructed with the aid of the active space method, which allows the electron correlation effects to be studied efficiently. The contributions of the electron correlation and the Breit interaction to the transition properties are analyzed in detail. It is found that the two-electron one-photon (TEOP) transition is correlation sensitive. The Breit interaction and electron correlation both contribute significantly to the radiative transition properties of the double K hole state of the He-like ions. Good agreement between the present calculation and previous work is achieved. The calculated data will be helpful to future investigations on double K hole decay processes of He-like ions.

Investigation of TEOP transitions in dielectronic recombination with H-like ions

SynopsisWe consider theoretically the process of dielectronic recombination (DR) with H-like ions where two-electron one-photon (TEOP) transitions take place. We focus our attention on the channel with transitions to the ground state of the He-like ions and emission of Kαα photon. Total and differential cross sections of DR with TEOP are calculated for wide range of H-like ions: from B4+ to Xe53+. The resonant Fano-like structure of the cross section is observed. The resonant energies, widths and TEOP transition probabilities are calculated.

The radiative decay process of 2s2p configuration of He-like ions

SynopsisThe electron correlation effects are crucial to the two-electron one-photon transition of double K hole excited state. Appropriate correlation model was constructed to investigate this process of 11 selected He-like ions of Z from 10 to 47. Good agreement to the previous work and some new transition data were obtained.

Anomalously strong two-electron one-photon X-ray decay transitions in CO caused by avoided crossing.

The unique opportunity to study and control electron-nuclear quantum dynamics in coupled potentials offered by the resonant inelastic X-ray scattering (RIXS) technique is utilized to unravel an anomalously strong two-electron one-photon transition from core-excited to Rydberg final states in the CO molecule. High-resolution RIXS measurements of CO in the energy region of 12–14 eV are presented and analyzed by means of quantum simulations using the wave packet propagation formalism and ab initio calculations of potential energy curves and transition dipole moments. The very good overall agreement between the experimental results and the theoretical predictions allows an in-depth interpretation of the salient spectral features in terms of Coulomb mixing of “dark” with “bright” final states leading to an effective two-electron one-photon transition. The present work illustrates that the improved spectral resolution of RIXS spectra achievable today may call for more advanced theories than what has been used in the past.

Radiative one- and two-electron transitions into the emptyKshell of He-like ions

The branching ratios between the single and double electron radiative transitions to empty K shell in He-like ions with 2s2p configuration are evaluated for 15 ions with 4{<=}Z{<=}26 using fully relativistic multiconfiguration Dirac-Fock wavefunctions in the active space approximation. The effects of configuration interaction and Breit contributions on the transition parameters have been analyzed in detail. Though the influence of Breit interaction on the electric dipole allowed one-electron radiative transitions is negligible, it substantially changes the spin-forbidden rates and the two-electron one-photon transition probabilities. Also, while the single electron transition rates are gauge independent, the correlated double-electron probabilities are found to be gauge sensitive. The probable uncertainties in the computed transition rates have been evaluated by considering the line strengths and the differences between the calculated and experimental transition energies as accuracy indicators. The present results are compared with other available experimental and theoretical data.

First Observation of Two-Electron One-Photon Transitions in Single-PhotonK-Shell Double Ionization

Experimental evidence for the correlated two-electron one-photon transitions (1s(-2)→2s(-1)2p(-1)) following single-photon K-shell double ionization is reported. The double K-shell vacancy states in solid Mg, Al, and Si were produced by means of monochromatized synchrotron radiation, and the two-electron one-photon radiative transitions were observed by using a wavelength dispersive spectrometer. The two-electron one-photon transition energies and the branching ratios of the radiative one-electron to two-electron transitions were determined and compared to available perturbation theory predictions and configuration interaction calculations.

Relativistic calculation of two-electron one-photon and hypersatellite transition energies for 12 ⩽ Z ⩽ 30 elements

Energies of two-electron one-photon transitions from initial double K-hole states were computed using the Dirac–Fock model. The transition energies of competing processes, the Kα hypersatellites, were also computed. The results are compared with experiment and to other theoretical calculations.

Observation of dielectronic recombination through two-electron–one-photon correlative stabilization in an electron-beam ion trap

Dielectronic recombination (DR) for He-like ${\mathrm{Ar}}^{16+}$ through both one-electron--one-photon and two-electron--one-photon (TEOP) stabilizations of Li-like states was studied with an electron-beam ion trap (EBIT). It turned out that this is an excellent method to investigate TEOP transitions. Its advantages are a high branching ratio for the TEOP transition and clean conditions under which spectator electrons are controlled. Further, state- and configuration-resolved KLL DR cross sections were obtained due to the unsurpassed electron energy resolution achieved in the EBIT in the energy range around 2 keV.

Two-electron one-photon transition relativistic calculations for low-Z elements

Energies of two-electron one-photon transitions from initial double K-hole states and the transition energies of competing processes, namely Kα hyper-satellites, were computed for low-Z elements, using the multi-configuration Dirac–Fock method. Transition rates are also evaluated.

Ar K X-ray production in slow, highly charged Ar q+(q = 8–18) + Ar collisions

In the present work, mechanisms of Ar K X-ray production have been investigated under low-energy Arq+ + Ar collisions in a wide range of the ion-charge states. Ar K X-rays have been observed as a function of the collision energy over (0.75–3.75)q keV/u and of the charge state over q = 8–16 of projectile Arq+ ions. If the L-shell vacancies become available (q = 9), Ar K X-ray yields are found to be enhanced roughly three orders of magnitude, compared with Ar8+ ions with no L-shell vacancy; to show some threshold; and to tend to quickly saturate at higher collision energies. The present analysis, based on the energy correlation diagrams of the quasi-molecules, suggests that Ar K X-rays originate entirely from target Ar atoms through promotion via the rotational coupling between 2pσ –2pπ molecular orbitals. Furthermore, the observed cross sections are found to increase nonlinearly with the projectile Arq+ ion charge q (q = 9). This can be understood because of the combined effects of two contributions: (i) the increased number of the L-shell vacancies of projectile Arq+ ions and (ii) the enhanced fluorescence yields of target Ar atom. In addition, Ar K X-rays have been observed under 2.5q keV/u Ar17+ and Ar18+ + Ar collisions and found to originate from the decay of K-shell vacancies initially present in the projectile Ar ions through electron capture into their highly excited states, followed by cascade down to the ground states. For the first time, though very weak, the X-rays due to the two-electron–one-photon transition, namely, K αα lines, have also been observed in bare Ar18+ ion collisions. PACS Nos.: 34.70+e, 32.80Rm

Radiative de-excitation of the 1s 2 2s3 p 3 P 0 level in beryllium-like ions: A competition between an E2 and a two-electron one-photon E1 transition

I have performed a complete Multi-Configuration Dirac-Fock calculation of the radiative de-excitation of the 1s22s3p3P0 level in beryllium-like ions. Initial and final wave functions are fully optimized, and include valence and core polarization correlation (Coulomb and Magnetic). Non-orthogonality between initial and final state spin-orbitals is exactly accounted for. I show that the main mode of de-excitation of the 1s22s3p3P0 level at high Z is an E2 transition to the 1s22s2p3P2 and that a two-electron one-photon E1 transition to the 1s22p2 3P1 plays an important role at low Z. The latter transition appears to be the difference of two large matrix elements which cancel almost exactly and thus has a very complicated Z dependence, which is studied in the present paper.

Two-electron one-photon x-ray transition energy in the Kr isoelectronic series.

Two-electron one-photon x-ray transition energies are calculated, using the Slater transition-state concept within the approximate local density-functional theory given by the X\ensuremath{\alpha} model, for the krypton atom and isoelectronic Rb, Yt, and Zr, respectively. The new theoretical results suggest that the transition energy is a linear function of the atomic number within the isoelectronic series.

Inner-shell two-electron—one-photon transition probabilities

A change-expansion method is used to calculate the probabilities of two-electron—one-photon 1 s -2 1S →(nl) -1 (n′l′) -1 1P electric dipole transitions when the final holes are in L and M shells. Computed branching ratios of KK → KL and KK → LL transitions agree with those of recent measurements.