Multichannel photoionization calculations using the relativistic random-phase approximation for outer shells in rare gases, neon, argon, krypton, and xenon, are presented. Total cross sections partial $\mathrm{ns}$ subshells determined compared with experiment alternative at low energies. Branching ratios of $^{2}P_{\frac{3}{2}}:^{2}P_{\frac{1}{2}}$ which sensitive to correlation effects presented experiment. Angular distribution asymmetry parameters $\ensuremath{\beta}$ each subshell found...

Eigenfunctions and eigenvalues of the relativistic no-pair Hamiltonian are determined for n=2 triplet states heliumlike ions with charges in range Z=5--100. The eigenfunctions expanded a basis two-electron wave functions constructed from Dirac-Coulomb orbitals restricted to finite cavity. matrix is evaluated Davidson's method then used determine lowest few eigenvalues. These calculations, which include Coulomb interaction retarded Breit interaction, corrected QED mass-polarization effects...

The relativistic random phase approximation RRPA is developed from linearized time-dependent Hartree-Fock theory. Applications of the resulting many-body equations to determine excitation energies and oscillator strengths along He, Be, Mg, Zn Ne isoelectronic sequences are discussed compared with other recent experimental theoretical work. multi-channel treatment photoionization described applications given total cross sections, branching ratios, angular distributions autoionizing resonances.

The Beutler-Fano autoionizing resonances in the rare-gas atoms argon, krypton, and xenon are studied using relativistic multichannel quantum-defect theory (MQDT). Dynamical parameters for MQDT analyses obtained from an ab initio relativistic-random-phase-approximation calculation. position profile of these good agreement with experimental measurements. Angular distribution spin polarization photoelectrons resonance regions also close recent

Energy shifts of radiative corrections in atoms due to perturbing potentials are calculated. The considered a constant magnetic field, the field nucleus, and Coulomb interaction from other electrons many-electron atoms.

The multiconfiguration Dirac-Fock (MCDF) method is used to calculate excitation energies, Land\'e g values, and hyperfine-structure (hfs) constants for the lowest multiplets of 4${f}^{N}$6${s}^{2}$ configurations neutral rare-earth atoms. Although no adjustable parameters are used, results in rather good agreement with experiment. calculated energies dipole hfs (using known moment values) differ from experiment by typically 5%, values 0.1%. Relative quadrupole determined muonic-atom or...

The self-energy corrections of order $\ensuremath{\alpha}$ to the $K$-electron binding energy in high-$Z$ atoms are studied numerically throughout range $Z=70\ensuremath{-}160$. Nuclear finite-size effects included electron wave functions and propagator avoid Coulomb singularity at $Z\ensuremath{\alpha}=1$. Denoting correction by $\ensuremath{\Delta}E=\frac{\ensuremath{\alpha}{(Z\ensuremath{\alpha})}^{4}F(Z\ensuremath{\alpha})m{c}^{2}}{\ensuremath{\pi}}$, it is found that...

Excitation energies and line strengths for the low-lying states of ions in Mg isoelectronic sequence are studied using relativistic multiconfiguration Hartree-Fock techniques. Line all possible electric dipole transitions between these calculated both length gauge velocity along from to ${\mathrm{U}}^{+80}$, results show good agreement two forms strength cases considered. At low $Z$, present work with other recent theoretical calculations. The this expected give accurate excitation at high...

We present a theoretical study of O(ka) and O(k2a2) corrections to the dipole approximation in photoionization rare gas atoms, where k is magnitude photon wave vector radius ionized subshell. In approximation, photoelectron angular distribution characterized by single parameter β. The are two parameters γ δ, three λ, μ, ν, constrained relation λ + μ ν = 0 correction Δβ Formulas given for non-dipole terms reduced matrix elements electric magnetic multipole operators. Tables graphs seven...

Term energies are determined for the ground state and n=2 singlet states of heliumlike ions with nuclear charges in range 4\ensuremath{\le}Z\ensuremath{\le}92. These calculations based on relativistic no-pair Hamiltonian which includes both Coulomb interaction retarded Breit interaction. Single-particle wave functions expanded a B-spline basis constructed from Dirac-Coulomb orbitals restricted to finite cavity. The matrix is evaluated Davidson's method used determine lowest few eigenenergies...

The effect of $4f$ orbital collapse on the spectra Xe-like ions in region $4d\ensuremath{\rightarrow}nf,\ensuremath{\epsilon}f$ excitations is studied with use a term-dependent Hartree-Fock technique. We find that strongly term dependent, and appearance intense absorption lines observed ${\mathrm{Ba}}^{2+}$ spectrum due to partial $4d\ensuremath{\rightarrow}f^{1}P$ channel. also show after completely collapsed for high degrees ionization along isoelectronic sequence, bulk oscillator...

A large discrepancy between Dirac-Fock calculations and experiment for the spin-orbit splitting, $^{2}P_{\frac{1}{2}}\ensuremath{-}^{2}P_{\frac{3}{2}}$, in ground states of B- F-like ions is resolved. The arises from spurious terms which are inherent relativistic self-consistent-field procedure. Removal these substantially improves agreement theory on splitting.

The hyperfine-induced $2s2p\phantom{\rule{0.3em}{0ex}}^{3}P_{0}--2{s}^{2}\phantom{\rule{0.3em}{0ex}}^{1}S_{0}$ transition rate for Be-like $^{47}\mathrm{Ti}^{18+}$ was recently measured in a storage-ring experiment by Schippers et al. [Phys. Rev. Lett. 98, 033001 (2007)]. value of $0.56(3)\phantom{\rule{0.3em}{0ex}}{\mathrm{s}}^{\ensuremath{-}1}$ is almost 60% larger than the theoretical $0.356\phantom{\rule{0.3em}{0ex}}{\mathrm{s}}^{\ensuremath{-}1}$ from multiconfiguration Dirac-Fock...

It is confirmed that the 3489-\AA{} transition observed in beam-foil excited lithium spectra originates from negative ion. most probably $1s2s2{p}^{2}^{5}P\ensuremath{-}1s2{p}^{3}^{5}S^{\ensuremath{\circ}}$, as suggested by Bunge. A new electric field acceleration technique provides identification of charge state emitting The decay curve a cascade-free single exponential. polarization and beam energy dependence light yield have also been measured. has identified heavier isoelectronic ions.

Under suitable conditions, relativistic corrections to the interaction of a photoelectron with its parent ion are enhanced, giving rise large anisotropic final-state effects which can be observed in angular distribution. The particular example $5s\ensuremath{\rightarrow}\ensuremath{\epsilon}p$ photoionization Xe is considered detail. It shown that asymmetry parameter $\ensuremath{\beta}$ reduced by factor 9 from nonrelativistic value 2 near $5s$ "Cooper minimum," so energy dependence becomes...

A QED approach to the calculation of spectra lithium isoelectronic sequence is implemented. modified Furry representation based on Kohn-Sham potential used evaluate all one- and two-photon diagrams with exception two-loop Lamb shift. Three-photon are estimated Hamiltonian methods. After incorporating recent calculations shift recoil corrections, a comprehensive tabulation $2s$, $2{p}_{1/2}$, $2{p}_{3/2}$ energy levels as well $2s--2{p}_{1/2}$ $2s--2{p}_{3/2}$ transition energies for...

QED effects associated with the electron self-energy and vacuum polarization are calculated in non-Coulomb potentials for atomic states principal quantum numbers 1 2. We consider Coulomb potential finite nuclear size incorporated using core-Hartree potential, a local version of Hartree-Fock potential. The calculations carried out ions charges range Z=60--90. For size, substantial discrepancies an earlier tabulation found. Radiative corrections lithiumlike uranium comparison experiment is made.

Calculations of the screened electron self-energy are carried out in local central potentials that approximate a Hartree-Fock potential. The resulting energy corrections combined with vacuum-polarization calculations and used to predict Lamb shift for n=2 states lithiumlike uranium, n=3 sodiumlike platinum, n=4 copperlike gold. theoretical values found be good agreement inferred from experiments.

Theoretical photoionization cross sections, angular distributions, and spin-polarization parameters for outer $\mathrm{ns}$ $(n\ensuremath{-}1)d$ subshells of the group-$\mathrm{II}B$ elements zinc, cadmium, mercury are determined above their respective thresholds. Account is taken electron-electron correlation spin-orbit interaction by means relativistic random-phase approximation. Comparisons made with previous theoretical work available experimental measurements.

Photoionization of the inner $4d$ shells for Xe, ${\mathrm{Cs}}^{+}$, ${\mathrm{Ba}}^{2+}$, and ${\mathrm{La}}^{3+}$ are studied with use relativistic random-phase approximation. Total cross sections, partial cross-section branching ratios, angular-distribution asymmetry parameters calculated, their systematic trends along isoelectronic sequence studied. Important dynamic effects electron correlations obtained from an eigenchannel analysis involving eigenquantum defects, eigendipole...

A version of quantum-defect theory appropriate to the analysis spectra highly ionised atoms is obtained from single-electron Dirac equation. Quantum defects mu n are defined as principal quantum number increases along Rydberg series using Sommerfeld's relativistic one-electron energy level formula. Considering analytic properties solutions equation, authors establish that can be extended smoothly away bound-state energies just in non-relativistic theory. Moreover, ( epsilon ) analytically...