States In Li-like Ions Research Articles

QED theory of the specific mass shift in few-electron atoms

The quantum electrodynamics formalism to treat the interelectronic-interaction correction of first order in $1/Z$ to the two-electron part of the nuclear recoil effect on binding energies in atoms and ions is developed. The nonperturbative in $\alpha Z$ calculations of the corresponding contribution to the energies of the $1s^2$ state in He-like and the $1s^2 2s$ and $1s^2 2p_{1/2}$ states in Li-like ions are performed in the range $Z=5-100$. The behavior of the two-electron part of the nuclear recoil effect beyond the lowest-order relativistic approximation as $Z$ grows is studied.

Relativistic many-body calculations of dielectronic satellite spectra created by autoionizing 1s2l2l′ states in Li-like ions

Relativistic many-body perturbation theory, including the Breit interaction, is used to evaluate energy levels, radiative matrix elements and autoionization rates for 1s2l2l′ states of lithium-like Mo39 +, Pr56 +, W71 + and Hg77 +. Radiative and non-radiative data are combined to obtain branching ratios, intensities and effective emission rate coefficients of dielectronic satellite lines. Relative intensity factors are shown graphically for the 1s2l′2l″–1s22l radiative transitions in lithium-like ions with nuclear charges Z ranging from 6 to 100; however, our emphasis here is on dielectronic recombination rates in the four lithium-like ions listed above. Such data, for high-Z ions in particular, are relevant to spectroscopic diagnostics of very high-temperature plasmas including future experiments at the International Thermonuclear Experimental Reactor.

Spectral transitions from the Rydberg autoionization states of a Li-like Mg X ion

Satellite lines caused by radiative transitions from the Rydberg autoionization states of a Li-like Mg X ion in a plasma heated by radiation from a XeCl and a Nd laser are identified for the first time, and their wavelengths are measured precisely. Comparison of the experimental data with the atomic structures calculated by the method of relativistic perturbation theory shows that the accuracy of calculations of the energy of autoionization states is rather high even without the use of any semiempirical corrections and is of the order of 0.06%. The experimentally measured wavelengths can be used for a semiempirical estimate of the value of the leading order of perturbation theory among the orders that were neglected in calculations. It is shown that the simulation of the population kinetics of Rydberg autoionization states of Li-like ions in a dense plasma should take into account all possible channels of dielectronic capture, in particular, from the excited states of a He-like ion. The precision experimental wavelengths obtained for satellites of the Hes and Heγ lines of the Mg XI ion make possible to use these satellites as reference lines in studies of complicated spectra of multielectron ions.

Contribution of three-electron diagrams of two-photon exchange to the energy of 2s, 2p 1/2, and 2p 3/2 states of Li-like multiply charged ions

The contribution of three-electron diagrams of two-photon exchange to the energy of 2s, 2p 1/2, and 2p 3/2 states of Li-like ions is calculated. The consistent quantum-electrodynamic calculation is performed for the nuclear charge Z varying over a wide range with the correction for the finite size of the nucleus taken into account. All the contributions to the energy of the 2p 1/2−2s transition in Li-like ions with Z≥18 calculated to date are collected.

Dielectronic recombination satellite transitions in dense plasmas

Radiative and dielectronic recombination of multiply charged many-electron ions in high-temperature plasmas are usually treated as independent, non-interfering processes. A projection-operator and resolvent-operator approach has been developed to provide a fundamental, unified quantum-mechanical description of the combined electron–ion photo-recombination process. This ordinary Hilbert-space approach provides a valid description in low-density electron–ion beam interactions or in low-density plasmas. By means of the Hebrew University Lawrence Livermore Atomic Code (HULLAC), cross sections for photo-recombination of He-like ions through autoionizing states in Li-like ions have been obtained. For certain transitions, interference effects are predicted in the form of radiatively modified, asymmetric satellite cross-section profiles (or spectral line shapes). A density–matrix formulation has been developed for high-density plasmas, for which collisional and radiative relaxation processes can play an important role. Using Liouville-space projection-operator techniques, collisional and radiative relaxation processes (including cascades) are incorporated on an equal footing and in a self-consistent manner with autoionization and radiative emission. Both time-independent (resolvent-operator) and time-dependent (equation-of-motion) formulations are developed. The density–matrix approach provides a comprehensive description of the broadening of dielectronic satellite spectral lines due to autoionization processes, radiative transitions, electron–ion collisions, and electric and magnetic fields. We plan to adapt HULLAC so that the various elementary electron–ion collisional and radiative transition amplitudes can be used as input data in a generalized collisional-radiative model based on the density–matrix formulation. By means of the density–matrix approach, radiation processes involving resonant and non-resonant transitions in a diverse class of quantized electronic systems can be treated within the context of a single quantum statistical formulation.

Calculation of mass polarization for the and states in Li-like ions

Mass polarization arises from a correlation between electronic momenta. In Li-like systems, the effect of core electron correlation dominates. The mass polarization for the and states in B III-Ne VIII is calculated with the use of configuration interaction (CI) wavefunctions. Its dependence on the nuclear charge Z and the atomic states is then studied. The effect of core electron correlation is clearly illustrated with a simple CI wavefunction.

Effects of relativity on multiplet splitting and decay rates of the1s2p2configuration of Li-like ions

Properties of the $1s2{p}^{2}$ states of Li-like ions are calculated relativistically for $6\ensuremath{\le}Z\ensuremath{\le}30$, with particular attention to the effects of the Breit interaction on multiplet splitting and the radiationless transitions through which these states decay. The full Breit interaction (magnetic and retardation terms) is included in calculating fine structure. Transition rates are computed in relativistic intermediate coupling with configuration interaction. Both the spin-orbit and magnetic interactions are incorporated in the calculations. Results are compared with earlier calculations and with experiment, and the physics of observed relativistic and configuration-interaction effects is discussed.