C. Harabati

Combining configuration interaction with perturbation theory for atoms with a large number of valence electrons

A version of the configuration interaction (CI) method is developed which treats highly excited many-electron basis states perturbatively, so that their inclusion does not affect the size of the CI matrix. This removes, at least in principle, the main limitation of the CI method in dealing with many-electron atoms or ions. We perform calculations of the spectra of iodine and its ions, tungsten, and ytterbium as examples of atoms with open

Identification of atoms that can bind positrons

s, p, d

Electron recombination, photoionization, and scattering via many-electron compound resonances

, and

Chaos-induced enhancement of resonant multielectron recombination in highly charged ions: Statistical theory

f

Erratum: Relations between matrix elements of different weak interactions and interpretation of the parity-nonconserving and electron electric-dipole-moment measurements in atoms and molecules [Phys. Rev. A84, 052108 (2011)]

shells. Good agreement of the calculated data with experiment illustrates the power of the method. Its advantages and limitations are discussed.

Relativistic linearized coupled-cluster single-double calculations of positron-atom bound states

Calculations of the positron binding energies to all atoms in the periodic table are presented and atoms where the positron-atom binding actually exists are identified. The results of these calculations and accurate calculations of other authors (which existed for several atoms only) are used to evaluate recommended values of the positron binding energies to the ground states of atoms. We also present the recommended energies of the positron excited bound levels and resonances (due to the binding of positron to excited states of atoms) which can not emit positronium and have relatively narrow widths. Such resonances in positron annihilation and scattering may be used to measure the positron binding energy.

Effect of nuclear quadrupole moments on parity nonconservation in atoms

Highly excited eigenstates of atoms and ions with open f shell are chaotic superpositions of thousands, or even millions, of Hartree-Fock determinant states. The interaction between dielectronic and multielectronic configurations leads to the broadening of dielectronic recombination resonances and relative enhancement of photon emission due to opening of thousands of radiative decay channels. The radiative yield is close to 100% for electron energy 1 eV and rapidly decreases for higher energies due to opening of many autoionization channels. The same mechanism predicts suppression of photoionization and relative enhancement of the Raman scattering. Results of our calculations of the recombination rate are in agreement with the experimental data for W 20+ and Au 25+ .

Electron recombination with tungsten ions with open f-shells

A statistical theory of resonant multielectron recombination based on properties of chaotic eigenstates is developed. The level density of many-body states increases exponentially with the number of excited electrons. When the residual electron-electron interaction exceeds the interval between these levels, the eigenstates (called compound states or compound resonances if these states are in the continuum) become “chaotic” superpositions of large numbers of Hartree-Fock configurational basis states. This situation takes place in some rare-earth atoms and many open-shell multiply charged ions excited in the process of electron recombination. Our theory describes resonant multielectron recombination via dielectronic doorway states leading to such compound resonances. The result is a radiative capture cross section averaged over a small energy interval containing several compound resonances. In many cases individual resonances are not resolved experimentally (since the interval between them is small, e.g., � 1 meV, possibly even smaller than their radiative widths), therefore, our statistical theory should correctly describe the experimental data. We perform numerical calculations of the recombination cross sections for tungsten ions W q+ , q = 18–25. The recombination rate for W 20+ measured recently [Phys. Rev. A 83, 012711 (2011)] is 10 3 greater than the direct radiative recombination rate at low energies, and our result for W 20+ agrees with the measurements.

Effects of Lorentz-symmetry violation on the spectra of rare-earth ions in a crystal field

The relations between matrix elements of different P- and T-odd weak interactions are derived. We demonstrate that similar relations hold for parity nonconserving (PNC) transition amplitudes and electron electric dipole moments (EDM) of atoms and molecules. This allows to express P- and T-odd effects in many-electron systems caused by different symmetry-breaking mechanisms via each other using simple analytical formulas. We use these relations for the interpretation of the anapole moment measurements in cesium and thallium and for the analysis of the relative contributions of the scalar-pseudoscalar CP-odd weak interaction and electron EDM to the EDM of Cs, Tl, Fr and other atoms and many polar molecules (YbF, PbO, ThO, etc.). Model-independent limits on electron EDM and the parameter of the scalar-pseudoscalar CP-odd interaction are found from the analysis of the EDM measurements for Tl and YbF.

Periodic table of positronic atoms

Relativistic linearized coupled-cluster single-double approximation with third-order corrections is used to calculate positron-atom bound states. The method is tested on closed-shell atoms such as Be, Mg, Ca, Zn, Cd, and Hg, where a number of accurate calculations are available. It is then used to calculate positron binding energies for a range of open-shell transition metal atoms from Sc to Cu, from Y to Pd, and from Lu to Pt. These systems possess Feshbach resonances, which can be used to search for positron-atom binding experimentally through resonant annihilation or scattering.