F. Parente

Cross Sections for K-Shell Ionization of Atoms by Electron Impact

The relativistic version of the binary-encounter Bethe (BEB) model is used to calculate cross sections for K-shell ionization of atoms by electron impact. The BEB model requires only two atomic constants, the binding energy and kinetic energy of the K electrons. These constants are listed for carbon to antimony. Comparisons with available experimental data on N, O, Na, Al, Cl, Ca, Cu, Se and Sb show good agreement. The K-shell ionization cross sections for C, Mg, P, S, Cr, As and Cd are tabulated.

L x-ray satellite energies

Abstract Theoretical energies are tabulated for the L x-ray satellites that arise from electric dipole and quadrupole transitions in the presence of one spectator hole in the M- or N-shell. Results are listed for 11 elements with atomic numbers 65 ≤ Z ≤ 95. The computations are relativistic and include quantum-electrodynamic corrections. Subsidiary tables list the Coulomb and Breit interaction energies for double-hole states and the relative x-ray intensities of double-hole multiplet states.

Interpretation of x-ray spectra emitted by Ar ions in an electron-cyclotron resonance ion source

We examine the most important processes leading to the creation of excited states from the ground configurations of Ar8+ to Ar16+ ions in an electron-cyclotron resonance ion source, which lead to the emission of K x-ray lines. Theoretical values for inner-shell excitation and ionization cross sections, including double KL ionization, transition probabilities and energies for the de-excitation processes, are calculated in the framework of the multi-configuration Dirac-Fock method. With reasonable assumptions about the electron energy distribution, a theoretical Kα x-ray spectrum is obtained, which reproduces very closely a recent experimental result.

RELATIVISTIC 2S1/2 (L1) ATOMIC SUBSHELL DECAY RATES AND FLUORESCENCE YIELDS FOR YB AND HG

De-excitation characteristics of 2s1/2 atomic hole states are poorly known. Measurements are hampered by the fact that the K-L1 radiative decay is dipole-forbidden in the non-relativistic limit, precluding standard coincidence experiments. Calculations call for state-of-the-art approaches. We report results of radiative and radiationless transition rates to L1 vacancy states carried out by two independent methods, i.e., a Dirac-Fock approximation and a second-order relativistic many-body approach. Calculations were performed for the elements Yb and Hg. Comparisons are made with measurements and with other theoretical results. Disagreement between experimental fluorescence yields and between experiment and theory persist even with the present, more advanced, methods.

Relativistic correlation correction to the binding energies of the ground configuration of beryllium-like, neon-like, magnesium-like and argon-like ions

Abstract.Total electronic correlation corrections to the binding energies of the isoelectronic series of beryllium, neon, magnesium and argon, are calculated in the framework of relativistic multiconfiguration Dirac-Fock method. Convergence of the correlation energies is studied as the active set of orbitals is increased. The Breit interaction is treated fully self-consistently. The final results can be used in the accurately determination of atomic masses from highly charged ions data obtained in Penning-trap experiments.

Resonance effects on the two-photon emission from hydrogenic ions

A theoretical study the all two-photon transitions from initial bound states with ni = 2, 3 in hydrogenic ions is presented. High-precision values of relativistic decay rates for ions with nuclear charge in the range 1 =< Z =< 92 are obtained through the use of finite basis sets for the Dirac equation constructed from B-splines. We also report the spectral (energy) distributions of several resonant transitions, which exhibit interesting structures, such as zeroes in the emission spectrum, indicating that two-photon emission is strongly suppressed at certain frequencies. We compare two different approaches (the Line Profile Approach (LPA) and the QED approach based on the analysis of the relativistic two-loop self energy (TLA)) to regularize the resonant contribution to the decay rate. Predictions for the pure two-photon contributions obtained in these approaches are found to be in a good numerical agreement.

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.

Satellite structure of Lα1 of iridium, gold and uranium

Assuming the shake-off process and Coster-Kronig theory of the origin of the satellites accompanying L alpha 1, the separations and relative intensities of these satellites are calculated for 77Ir, 79Au and 92U. Contours of the satellite structure are obtained and compared with the results of Richtmyer and Ramberg for gold.

Relativistic MCDF calculation of Kβ/Kα intensity ratios

The multiconfiguration Dirac-Fock method was used to compute the relative intensities of Kβ to Kα x-rays (Kβ/Kα) for several elements in the range 20≤Z≤80. We investigate the effect of the Breit interaction on Kβ/Kα ratios and find it negligible. The results are compared with experimental data and other theoretical calculations.

Hyperfine Quenching of the 3s23p63d4 J = 4 Level in Titaniumlike Ions

In this paper we present a calculation of the lifetime of the J = 4 level in the 3d4 ground configuration of titaniumlike ions. Hyperfine quenching changes this lifetime by several orders of magnitude, the final result being strongly dependent on the nuclear electric-quadrupole moment. This can lead to a new method of obtaining values of nuclear electric-quadrupole moments for some stable isotopes.