Relativistic Quantum Defect Research Articles

OPTIMIZED QUANTUM DEFECT METHOD IN RELATIVISTIC THEORY OF SPECTRA OF LI-LIKE MULTICHARGED IONS

The relativistic theory of radiative transitions using the general relativistic quantum defect approximation (GDA) was also used to study the wavelengths and oscillator strengths for the 1s22s (2S1/2) → 1s23p (2P1/2) transitions in Li-like multicharged ions with a nuclear charge Z= 14-70. and. The obtained results were compared with available theoretical and experimental (summarized) data. An important point is related to the accurate accounting of the complex contributions of the exchange-correlation (polarization) effect and the use of an efficient single-quasi-particle representation based on the general relativistic approximation of the quantum defect, which significantly ensures a physically reasonable agreement between the theory and the experiment.

Wigner–Eisenbud–Smith photoionization time delay due to autoioinization resonances

An empirical ansatz for the complex photoionization amplitude and Wigner–Eisenbud–Smith time delay in the vicinity of a Fano autoionization resonance are proposed to evaluate and interpret the time delay in the resonant region. The utility of this expression is evaluated in comparison with accurate numerical calculations employing the ab initio relativistic random phase approximation and relativistic multichannel quantum defect theory. The indisputably good qualitative agreement (and semiquantitative agreement) between corresponding results of the proposed model and results produced by the ab initio theories proves the usability of the model. In addition, the phenomenology of the time delay in the vicinity of multichannel autoionizing resonances is detailed.

QUANTUM DEFECT APPROXIMATION IN THEORY OF RADIATIVE TRANSITIONS IN SPECTRUM OF Li-LIKE CALCIUM

The combined relativistic quantum defect approximation and relativistic many-body perturbation theory with the zeroth order optimized approximation are applied to studying the Li-like calcium oscillator strengths of radiative transitions from ground state to the Rydberg states. New element in our scheme is an implementation of optimized relativistic quantum defect approximation to an energy approach frames. Comparison of calculated oscillator strengths with available theoretical and experimental (compillated) data is performed and a number of oscillator strengths are presented firstly.

The relation between the wave functions of discrete and continuum spectra and the Fermi-Segre formula

One-electron wave functions of discrete and continuum spectra are usually normalized using different normalization conditions. A unified normalization based on the relativistic quantum defect theory is considered in this paper for both the discrete and continuum spectra. The radial wave functions normalized according to this procedure are virtually independent of quantum number n (i.e., of the energy) in the vicinity of the origin. This is demonstrated by the example of wave functions of a valence electron of the Sr+ ion calculated by the Dirac-Fock method. A relation between this normalization and the Fermi-Segre formula is obtained. A modified Fermi-Segre formula is proposed.

Autoionization resonances in the argon iso-electronic sequence

We report results of theoretical studies of 3s → np and 2s → np autoionization resonances, respectively, in the 3p and the 2p photoionization cross sections of a few members (Ar, K+, Ca2+, Fe8+, Zn12+, and Kr18+) of the argon isoelectronic sequence, within the framework of the relativistic random phase approximation and using the relativistic multichannel quantum defect theory. The present approach would enable analysis of complex atomic spectra especially of atomic and (or) ionic species that are found in stellar gases in a computationally economical way. The shape profiles of the autoionization resonances have been analyzed in the present work using appropriate Fano parameters. The quantum defects determined for some of the lower or intermediate excited states are found to be in good agreement with the experimental and (or) theoretical results.

Spontaneous radiative decay rates in Ga-like ions

The analysis of forbidden lines, such as E2 and M1, in the atomic spectra emitted by certain ions is important for the study of the plasma in astrophysical objects and fusion devices. Atomic data, such as wavelengths and transition rates for 4p3/2 → 4p1/2 emission lines in the gallium sequence have been calculated with the Relativistic Quantum Defect Orbital (RQDO) method. The present results are tested by comparison with other theoretical values available in the literature. The regularity of the transition intensities along the isoelectronic sequence for both (E2 and M1) lines, as well as their relative magnitude, are also analyzed. M1 transitions were found to dominate by at least a factor of ten times, being in many cases bigger that this. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2008

Complementary investigations using the MCDF and RQDO methods

AbstractTheoretical oscillator strengths for fine‐structure lines of electric dipole (E1) allowed transitions for a number of ions belonging to the Be, As, and Ge sequences, are reported. Both ab initio (multiconfiguration Dirac–Fock) and model potential (relativistic quantum defect orbital) techniques have been used. A comparative analysis of the two sets of f‐values, as well as with other data found in the literature, has been carried out. For most of the studied ions and transitions, the results achieved with the two methodologies are, overall, in rather good agreement. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005

Trends in E2 and M1 transition rates between 3p${_{{\mathsf{3/2}}}}$ and 3p${_{\mathsf{{1/2}}}}$ levels in 3s${^{\mathsf{2}}}$ 3p${^k}$ systems

The analysis of forbidden lines, such as E2 and M1, in the atomic spectra emitted by certain ions is important for the study of the plasma in astrophysical objects and fusion devices. Transition rates between 3p 3 / 2 and3p 1 / 2 levels in 3s 2 3p k ions that belong to the aluminium sequence have been calculated with the Relativistic Quantum Defect Orbital (RQDO) method. The present data are tested by comparison with other theoretical data available in the literature, and the regularity of the transition intensities along the isoelectronic sequence for both (E2 and Ml) lines, as well as their competition, are also analysed.

Intensities of E2 Spectral Lines in the Astrophysically Important Ion Mgii

Relativistic quantum defect orbital (RQDO) formalism is applied to the study of forbidden transitions in the astrophysically important ion Mg II. The RQDO calculations have been performed in the LSJ coupling scheme on E2 inter- and intraconfiguration transitions. Line strengths, oscillator strengths, and Einstein coefficients are reported and compared with the data found in the literature. A good agreement with the comparative data as well as the expected systematic behavior of the RQDO line strengths along the spectral series confirms earlier conclusions about the quality of the RQDO wave functions. The E2 spectrum of Mg II is graphically shown.

Spectroscopy of forbidden transitions in ions of astrophysical interest

The spectroscopic study of forbidden transitions in ions of astrophysical interest has been performed using an extension of the well-established relativistic quantum defect orbital (RQDO) method. The method has so far proved to be a very useful tool for predicting a large body of electron transition probabilities, and other related properties. The RQDO method has been applied to the study of E2 transitions in the spectra of ions relevant in astrophysics, such as Ti XII, Fe XVI, Co XVII and Ni XVIII.

MCDF and RQDO study of the fine-structure lines of transition arraynp$^2 \to n$p $(n+1)$s in isoelectronic atomic systems

Relativistic calculations of electric dipole (E1) allowed transition for a number of ions in the germanium sequence have been performed. Oscillator strengths for fine-structure transitions within the 4p 2 -4p5s array have been calculated with both the Multiconfigurational Dirac-Fock (MCDF) approach and the Relativistic Quantum Defect Orbital (RQDO) method. The results are analysed on the grounds of the theoretical data available in the literature. Also, a comparative analysis with the homologous silicon sequence is made. The spectra of systems such as Mo XI are important in the context of plasma physics and thermonuclear fusion measurements.

Atomic data for M1 and E2 emission lines in the potassium isoelectronic sequence

Relativistic Quantum Defect Orbital (RQDO) calculations of transition probabilities for E2 and M1 forbidden transition in the potassium sequence have been performed. Intensities for the higher ions are reported, to our knowledge, for the first time, as they are potentially important for the study of the plasma in astrophysical objects and fusion devices.

Forbidden emission coefficients for intraconfigurationtransitions 2p3/2→2p1/2 along the boron sequence

Relativistic quantum defect orbital calculations oftransition probabilities for E2 and M1 transitions in the boronsequence have been performed. The present data are analysed onthe grounds of other theoretical data available in theliterature. Regularities in the transition intensities alongthe isoelectronic sequence for each line are also tested. Theanalysis of forbidden lines in the spectrum is important forthe study of the plasma in astrophysical objects and fusiondevices.

Systematic trends in E2 transitions along the sodium isoelectronic sequence

AbstractOscillator strengths for E2‐forbidden spectral lines of sodium‐isoelectronic ions, from K IX (Z=19) to Cs XLV (Z=55), have been calculated in the LS‐coupling scheme using the relativistic quantum defect orbital (RQDO) method. The study of many of these sodiumlike ions is relevant to processes in fusion devices and in astrophysical objects. Our data are compared with the very few results available, and their systematic trend is analyzed for np 2P0–n′f 2F0 transitions. The influence of relativistic effects in E2 transitions along this sequence is also discussed. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001

Relativistic quantum defect orbital study of forbidden transitions in Co16+

Theoretical line strengths and transition probabilities for electric quadrupole (E2) transitions between levels belonging to several important configurations of Co 16+ are reported. The calculations have been carried out with the Relativistic Quantum Defect Orbital (RQDO) method. A general good accord between the present results and some earlier theoretical data is found. Some of the E2 transition probabilities are reported for the first time. The correct systematic behaviour of the RQDO line strengths along the spectral series is reproduced by the present results in the absence of configuration mixing. This semiempirical method appears to adequately describe E2 transitions in this medium- Z atomic system.

Regularities along spectral series in forbidden transitions of Ti$\mathsf{^{11+}}$

Electric quadrupole (E2) transitions of Ti 11+ have been computed with the Relativistic Quantum Defect Orbital (RQDO) method. The correctness of our predictions has been analysed through the inspection of the systematic behaviour of the RQDO line strengths along the spectral series, and by the excellent accord of the SRQDO results with the scarce data available in the literature. Ti 11+ being one of the ions of the iron group, the study of its forbidden lines is of particular interest. The spectrum of this ion is important for the study of plasmas in astrophysical objects and fusion devices.

E2 transitions in Ti XII. Relativistic calculations

Plasma spectra, in astrophysical objects and fusion devices,exhibit forbidden lines of alkali-like ions. Ions belonging tothe iron group are particularly important. Electric quadrupole(E2) transitions of Ti XII have been computed in this paper with thesemiempirical relativistic quantum defect orbital (RQDO)formalism. The RQDO results are found to be in good agreementwith the scarce source data available in the literature. Thequality of the RQDO wavefunctions is also analysed throughinspection of the systematic behaviour of the RQDO linestrengths along the spectral series. We are hopeful that thenon-previously-existing S-values calculated in this paper mayoffer potential usefulness in astrophysics and fusion research.

Spectral properties of neutral selenium and tellurium. A relativistic treatment

Oscillator strengths for fine-structure transitions in the complex atomic systems, neutral selenium, and tellurium, are reported. The calculations were carried out using the relativistic quantum defect orbital method. The resulting oscillator strengths are analyzed in terms of other theoretical and experimental data. In addition, to estimate the correctness of our oscillator strengths for these species, we have also analyzed the regularities complied by the calculated f-values. © 2001 John Wiley & Sons, Inc. Int J Quant Chem, 2001

Intensities for Transitions Involving Highly Excited States of Nii: A Relativistic Treatment

Astrophysically relevant transitions involving excited states in singly ionized nitrogen have been studied, some of them for the first time in the LK-coupling scheme. The Relativistic Quantum Defect Orbital method has been employed. Oscillator strengths and transition probabilities for the fine-structure lines of a number of transition arrays are reported and analyzed.

Electric quadrupole transitions in Ni XVIII

Relativistic Quantum Defect Orbital (RQDO) calculations have been performed in the LS coupling scheme on electric quadrupole (E2) transitions between levels belonging to several astrophysically important con- gurations of Ni XVIII. A number of line strengths are reported and compared with the ones found in the litera- ture. A good agreement with the comparative data as well as the expected systematic behaviour of the RQDO line strengths along the spectral series conrms earlier conclu- sions about the quality of the RQDO wavefunctions.