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Stark-induced amplitudes for the 6P{sub 1/2}-7P{sub 1/2} transition in Tl I are calculated using the relativistic singles-doubles (SD) approximation in which single and double excitations of Dirac-Hartree-Fock levels are summed to all orders in perturbation theory. Our SD values {alpha}{sub S}=368a{sub 0}{sup 3} and |{beta}{sub S}|=298a{sub 0}{sup 3} are in good agreement with the measurements {alpha}{sub S}=377(8)a{sub 0}{sup 3} and {beta}{sub S}=313(8)a{sub 0}{sup 3} by D. DeMille, D. Budker, and E. D. Commins [Phys. Rev. A 50, 4657 (1994)]. Calculations of the Stark shifts in the 6P{sub 1/2}-7P{sub 1/2} and 6P{sub 1/2}-7S{sub 1/2} transitions are also carried out. The Stark shifts predicted by our calculations agree with the most accurate measured values within the experimental uncertainties for both transitions.

The blackbody radiation (BBR) shift is an important systematic correction for the atomic frequency standards realizing the SI unit of time. Presently, there is controversy over the value of the BBR shift for the primary 133Cs standard. At room temperatures, the values from various groups differ at the 3x10(-15) level, while modern clocks are aiming at 10(-16) accuracies. We carry out high-precision relativistic many-body calculations of the BBR shift. For the BBR coefficient beta at T=300 K, we obtain beta=-(1.710+/-0.006)x10(-14), implying 6x10(-17) fractional uncertainty. While in accord with the most accurate measurement, our 0.35% accurate value is in a substantial (10%) disagreement with recent semiempirical calculations. We identify an oversight in those calculations.

Relative intensities of dielectronic satellite lines determined by radiative transition probabilities and autoionization rates are calculated for transitions 1s2lnl'-1s2nl', 1s2lnl'-1s22l (n = 4-10, l = 0-3) for Li-like ions with Z = 5-54 by using the perturbation theory method (Z-expansion). Relativistic effects are taken into account by the Breit-Pauli operators. It was observed that the relative factor intensity changes very sharply with n and Z due to redistribution between contributions of relativistic and correlation effects.

Energies of 2s23l, 2s2p(1P)3l, 2s2p(3P)3l and 2p23l states (with l = s, p, d) for B-like Na are calculated. These perturbation-theory calculations make use of a frozen-core relativistic Hartree-Fock basis sets. The calculations include Coulomb and Breit contributions from first- and second-order diagrams for both diagonal and non-diagonal matrix elements. Corrections for the frequency-dependent Breit interaction are taken into account in lowest order and corrections for the Lamb shift are also included. Contributions from three-electron diagrams are compared with those from one- and two-electron diagrams. Comparisons are made with available experimental data; we find good agreement in most cases with experimental term-splitting values in ions with small nuclear charge.

The analysis of equilibrium conditions might be irrelevant to determine the importance of a certain set of atomic data. We show, that in non‐equilibrium and optically thick plasmas intercombination transitions between highly excited states as well as higher order dielectronic satellite transitions are of extraordinary importance for diagnostics. In optically thin equilibrium plasmas, however, they are almost negligible. Numerical examples are presented for neutral helium in attached/detached plasmas as well as for dense laser produced plasmas.

A finite-field scaling method is applied to evaluate the Lennard-Jones interaction constant ${C}_{3}$ for alkali-metal atoms. The calculations are based on the relativistic single-double approximation in which single and double excitations of Dirac-Hartree-Fock wave functions are included to all orders in perturbation theory.

To address the shortage of experimental data for electron spectra of triply-ionized rare earth elements we have calculated energy levels and lifetimes of 4f{n+1} and 4f{n}5d configurations of Nd IV (n=2), Pm IV (n=3), Sm IV (n=4), and Eu IV (n=5) using Hartree-Fock and configuration interaction methods. To control the accuracy of our calculations we also performed similar calculations for Pr III, Nd III and Sm III, for which experimental data are available. The results are important, in particular, for physics of magnetic garnets., 4 pages 1 table

The nuclear spin-dependent parity-nonconserving (PNC) interaction arising from a combination of the hyperfine interaction and the coherent, spin-independent, PNC interaction from Z exchange is evaluated using many-body perturbation theory. For the 6s{sub 1/2}-7s{sub 1/2} transition in {sup 133}Cs, we obtain a result that is about 40% smaller than that found previously by Bouchiat and Piketty [Phys. Lett. B 269, 195 (1991)]. Applying this result to {sup 133}Cs leads to an increase in the experimental value of nuclear anapole moment and exacerbates differences between constraints on PNC meson coupling constants obtained from the Cs anapole moment and those obtained from other nuclear parity violating experiments. Nuclear spin-dependent PNC dipole matrix elements, including contributions from the combined weak-hyperfine interaction, are also given for the 7s{sub 1/2}-8s{sub 1/2} transition in {sup 211}Fr and for transitions between ground-state hyperfine levels in K, Rb, Cs, Ba{sup +}, Au, Tl, Fr, and Ra{sup +}.

Energies of (3s2 3p6 3d9 4l4l'), (3s2 3p5 3d10 4l4l'), and (3s 3p6 3d10 4l4l') states for Cu-like ions with Z = 30 -100 are evaluated to second order in relativistic many-body perturbation theory (RMBPT) starting from a Ni-like Dirac-Fock potential. Second-order Coulomb and Breit-Coulomb interactions are included. Correction for the frequency-dependence of the Breit interaction is taken into account in lowest order. The Lamb shift correction to energies is also included in lowest order. Intrinsic particle-particle-hole contributions to energies are found to be 20-30% of the sum of one- and two-body contributions. Transition rates and line strengths are calculated for the 3l-4l' electric-dipole (E1) transitions in Cu-like ions with nuclear charge Z = 30 - 100. RMBPT including the Breit interaction is used to evaluate retarded E1 matrix elements in length and velocity forms. First-order RMBPT is used to obtain intermediate coupling coefficients and second-order RMBPT is used to calculate transition matrix elements. A detailed discussion of the various contributions to the dipole matrix elements and energy levels is given for copperlike tungsten (Z = 74). The transition energies used in the calculation of oscillator strengths and transition rates are from second-order RMBPT. Trends of the transition rates as functions of $Z$ are illustrated graphically for selected transitions. Comparisons are made with available experimental data. These atomic data are important in modeling of M-shell radiation spectra of heavy ions generated in electron beam ion trap experiments and in M-shell diagnostics of plasmas., Comment: 4 figures and 6 tables

Energies of 5l_j (l= s, p, d, f, g) and 4f_j states in neutral Ag and Ag-like ions with nuclear charges Z = 48 - 100 are calculated using relativistic many-body perturbation theory. Reduced matrix elements, oscillator strengths, transition rates and lifetimes are calculated for the 17 possible 5l_j-5l'_{j'} and 4f_j-5l_{j'} electric-dipole transitions. Third-order corrections to energies and dipole matrix elements are included for neutral Ag and for ions with Z60. Comparisons are made with available experimental data for transition energies and lifetimes. Correlation energies and transition rates are shown graphically as functions of nuclear charge Z for selected cases. These calculations provide a theoretical benchmark for comparison with experiment and theory., 8 pages

Energies, transition rates, and electron electric-dipole-moment (EDM) enhancement factors are calculated for low-lying states of Ce IV and Pr V using relativistic many-body perturbation theory. This study is related to recent investigations of the more complicated Gd IV ion, which is promising for electron EDM experiments. The ions Ce IV and Pr V both have a single valence electron, permitting one to carry out reliable ab initio calculations of energy levels, transition rates, and other atomic properties using well-developed computational methods.

This paper presents a detailed investigation of the temporal, spatial, and spectroscopic properties of L-shell radiation from 0.8 to 1.0 MA Mo x pinches. Time-resolved measurements of x-ray radiation and both time-gated and time-integrated spectra and pinhole images are presented and analyzed. High-current x pinches are found to have complex spatial and temporal structures. A collisional-radiative kinetic model has been developed and used to interpret L-shell Mo spectra. The model includes the ground state of every ionization stage of Mo and detailed structure for the O-, F-, Ne-, Na-, and Mg-like ionization stages. Hot electron beams generated by current-carrying electrons in the x pinch are modeled by a non-Maxwellian electron distribution function and have significant influence on L-shell spectra. The results of 20 Mo x-pinch shots with wire diameters from 24 to $62\ensuremath{\mu}\mathrm{m}$ have been modeled. Overall, the modeled spectra fit the experimental spectra well and indicate for time-integrated spectra electron densities between $2\ifmmode\times\else\texttimes\fi{}{10}^{21}$ and $2\ifmmode\times\else\texttimes\fi{}{10}^{22}{\mathrm{cm}}^{\ensuremath{-}3},$ electron temperatures between 700 and 850 eV, and hot electron fractions between 3% and 7%. Time-gated spectra exhibit wide variations in temperature and density of plasma hot spots during the same discharge.

The review of systematic investigations of X‐ray radiation properties of different clusters heated by short‐pulse (35–1100 fs) high‐intensive (1016– 1018 W/cm2) Ti:Sa laser radiation is presented. The cluster targets were formed by the adiabatic expansion in vacuum of an Kr or Ar gas jets produced by a pulsed valve with Laval or conical nozzles. The gas pressure is varied from 15 up to 100 bar. High spectrally (λ/δλ=4000–5000) and spatially (40–80 μm) resolved X‐Ray spectra near resonance lines (4‐2 transitions) of Ne‐like ions of Kr, H‐ and He‐like ions of Ar have been obtained and detailed spectroscopic analysis was consistent with a theoretical two‐temperature collisional‐radiative model of irradiated atomic clusters incorporating with an effects of highly energetic electrons. The role of laser prepulse for X‐ray intensity emission investigated in details. X‐ray spectra radiation from plasma with electron density more than 2×1022 cm−3 was observed. Big effect of fast electrons influence on the X‐ray emission of He‐like Ar and Ne‐like Kr spectra was demonstrated. Comparison of data obtained under various experimental conditions clearly showed that for increasing X‐ray output from plasma the most essential to increase size of clusters and has reasonable value of ps prepulse.

This paper presents a detailed investigation of the temporal, spatial, and spectroscopic properties of L-shell radiation from 0.8 to 1.0 MA Mo x pinches. Time-resolved measurements of x-ray radiation and both time-gated and time-integrated spectra and pinhole images are presented and analyzed. High-current x pinches are found to have complex spatial and temporal structures. A collisional-radiative kinetic model has been developed and used to interpret L-shell Mo spectra. The model includes the ground state of every ionization stage of Mo and detailed structure for the O-, F-, Ne-, Na-, and Mg-like ionization stages. Hot electron beams generated by current-carrying electrons in the x pinch are modeled by a non-Maxwellian electron distribution function and have significant influence on L-shell spectra. The results of 20 Mo x-pinch shots with wire diameters from 24 to 62 microm have been modeled. Overall, the modeled spectra fit the experimental spectra well and indicate for time-integrated spectra electron densities between 2 x 10(21) and 2 x 10(22) cm(-3), electron temperatures between 700 and 850 eV, and hot electron fractions between 3% and 7%. Time-gated spectra exhibit wide variations in temperature and density of plasma hot spots during the same discharge.

Rates and line strengths are calculated for the 2s22p53l3l' - 2s22p63l'' and 2s2p63l3l' - 2s22p63l'' electric-dipole (E1) transitions in Na-like ions with nuclear charges ranging from Z = 14 to 100. Relativistic many-body perturbation theory (RMBPT), including the Breit interaction, is used to evaluate retarded E1 matrix elements in length and velocity forms. The calculations start from a 1s22s22p6 Dirac-Fock potential. First-order RMBPT is used to obtain intermediate coupling coefficients and second-order RMBPT is used to calculate transition matrix elements. A detailed discussion of the various contributions to dipole matrix elements is given for sodiumlike copper (Z = 29). Transition energies used in the calculation of transition rates are from second-order RMBPT. Trends of transition rates as functions of Z are shown graphically for selected transitions., 9 pages and 5 figures

We have calculated energy levels and lifetimes of 4f7 and 4f6 5d configurations of Gd IV using Hartree-Fock and configuration interaction methods. This allows us to reduce significantly the uncertainty of the theoretical determination of the electron electric dipole moment (EDM) enhancement factor in this ion and, correspondingly, in gadolinium-containing garnets for which such measurements were recently proposed. Our new value for the EDM enhancement factor of Gd+3 is -2.2 +- 0.5. Calculations of energy levels and lifetimes for Eu~III are used to control the accuracy., Submitted to Phys. Rev. A 6 pages, 0 figures, 3 tables

Intense L x rays have been observed in $\ensuremath{\sim}2\ensuremath{-}\mathrm{k}\mathrm{e}\mathrm{V}/\mathrm{u} {\mathrm{Kr}}^{q+}$ $(q=27\char21{}33)$ ions colliding with various atom and molecule targets. These x rays are understood to originate from electron capture processes into high-Rydberg states of the projectile ion from the outermost shell of target where the captured electron cascades down into the vacant L shell of the ion, thus emitting L x rays. It has been found that the observed L x-ray spectra move toward higher energy as the ion charge (q) increases. The observed L x-ray spectra are compared with synthetic spectra using various models. It has been found that the L x-ray production cross sections obtained for ${\mathrm{Kr}}^{27+}$ ions are inversely proportional to the ionization energy of target, similar to those recently observed in K x rays produced from ions with K-shell vacancy, and correspond to roughly 40% of total electron capture cross sections, meanwhile the rest of the electron cascades into the metastable states and thus cannot decay within a viewing region of a Si(Li) x-ray detector.

Wavelengths and transition rates are given for E1 transitions between singlet S, P, D, and F states, between triplet S, P, and D states, and between triplet P and singlet S states in ions of astrophysical interest: helium-like carbon, nitrogen, oxygen, neon, silicon, and argon. All possible E1 transitions between states with J < 4 and n < 7 are considered. Energy levels and wave functions used in calculations of the transition rates are obtained from relativistic configuration-interaction calculations that include both Coulomb and Breit interactions., submitted to Astrophysical Journal

Strong L-shell x-ray emission has been obtained from Kr clusters formed in gas jets and irradiated by 60-500-fs laser pulses. Spectral lines from the F-, Ne- Na-, and Mg-like charge states of Kr have been identified from highly resolved x-ray spectra. Spectral line intensities are used in conjunction with a detailed time-dependent collisional-radiative model to diagnose the electron distribution functions of plasmas formed in various gas jet nozzles with various laser pulse durations. It is shown that L-shell spectra formed by relatively long nanosecond-laser pulses can be well described by a steady-state model without hot electrons when opacity effects are included. In contrast, adequate modeling of L-shell spectra from highly transient and inhomogeneous femtosecond-laser plasmas requires including the influence of hot electrons. It is shown that femtosecond-laser interaction with gas jets from conical nozzles produces plasmas with higher ionization balances than plasmas formed by gas jets from Laval nozzles, in agreement with previous work for femtosecond laser interaction with Ar clusters.

Excitation energies, oscillator strengths, and transition rates are calculated for (5d2+5d6s+6s2)--(5d6p+5d5f+6s6p) electric dipole transitions in Yb-like ions with nuclear charges Z ranging from 72 to 100. Relativistic many-body perturbation theory (RMBPT), including the retarded Breit interaction, is used to evaluate retarded E1 matrix elements in length and velocity forms. The calculations start from a [Xe]4f14 core Dirac-Fock potential. First-order RMBPT is used to obtain intermediate coupling coefficients, and second-order RMBPT is used to determine matrix elements. A detailed discussion of the various contributions to energy levels and dipole matrix elements is given for ytterbium like rhenium, Z=75. The resulting transition energies are compared with experimental values and with results from other recent calculations. Trends of excitation energies, line strengths, oscillator strengths, and transition rates as functions of nuclear charge Z are shown graphically for selected states and transitions. These calculations are presented as a theoretical benchmark for comparison with experiment and theory., Comment: 4 tables and 7 figures submittes to Physical Review A

An overview of the detailed spectroscopic analysis of more than fifty z-pinch shots at the Nevada Terawatt Facility is presented. Experimental x-ray spectra generated by Ti, Fe, Mo, W, and Pt z-pinches have been collected in wire implosions driven by a 0.7–1 MA current. Different configurations and masses of z-pinch loads are studied. In x-pinch experiments, pinhole images and damage to the anodes after shots evidence the presence of electron beams. Non-LTE collisional-radiative atomic kinetics models that include hot electrons have been developed and applied to interpret experimental x-ray spectra. In particular, diagnostics for K-shell spectra of Ti ions and L-shell spectra of Mo ions are presented.

Tungsten wire explosions are being intensively studied at Sandia National Laboratories. Any available x-ray spectral data accumulated in Z experiments with appropriate theoretical modeling can lead to better understanding of plasma evolution during a wire explosion. The present work focuses on the theoretical development of M-shell spectroscopy of W ions in the spectral range from 4 up to 8 A. The majority of line emissions in this spectral region is composed of 31 → 41′, 51″ transitions. Atomic data were calculated using Cowan and MBPT codes for all isoelectronic sequences contributing into this spectral range. The non-LTE kinetic model was developed based on these atomic data. The sensitivity of this model to the number of included ions, configurations and levels, the electron density, ionization balance, and electron distribution function is discussed. The complete modeling of this spectrum allows a detailed diagnostic of a hotter plasma core in z-pinch experiments involving heavy ions.

K x rays have been observed in electron capture processes of H-like ${\mathrm{Si}}^{13+},$ ${\mathrm{S}}^{15+},$ and ${\mathrm{Ar}}^{17+}(1s)$ ions colliding with various atom and molecule gas targets over the collision energy of $1--70$ $\mathrm{keV}/u.$ These K x rays are the final results of cascade-down to the ground ${(1s}^{2})$ state from highly excited states formed through electron capture. It has been found that at low energies $(l10$ $\mathrm{keV}/u)$ the cross sections for the production of K x rays are nearly constant, and decrease slowly when the collision energy is increased. The cross sections also have been found to increase roughly with the inverse square of the ionization energy of the targets. It is also noted that the intensity ratios of the $K\ensuremath{\beta}$ line to the $K\ensuremath{\alpha}$ line increase slightly as the ionization energy of the target increases, suggesting that an electron is captured in different $(n/)$ states in different targets. These ratios are found to decrease slightly as the collision energy increases. The measured K x-ray production cross sections also have been compared with total electron-capture cross sections based upon an empirical formula, and it has been found that, on average, roughly two-third of total electron capture processes result in K x-ray emission, with the remaining one-third ending at the metastable state level after electron capture without emitting K x rays.

Energies, transition probabilities, and lifetimes are calculated for ${3d}^{2}$ states in Ca-like ions with nuclear charges Z ranging from 22 to 100. Relativistic many-body perturbation theory (MBPT), including the Breit interaction, is used to evaluate retarded $M1$ and $E2$ matrix elements. The calculations start from a ${1s}^{2}{2s}^{2}{2p}^{6}{3s}^{2}{3p}^{6}$ Dirac-Fock potential. First-order perturbation theory is used to obtain intermediate coupling coefficients and second-order MBPT is used to determine matrix elements. Contributions from negative-energy states are included in the second-order $M1$ and $E2$ matrix elements. The resulting transition energies and lifetimes are compared with experimental values and with results from other recent calculations.

Excitation energies for $3l\ensuremath{-}{4l}^{\ensuremath{'}}$ particle-hole states of Ni-like ions are determined to second order in relativistic many body perturbation theory. The calculations start from a closed-shell Dirac-Fock potential, and include second-order Coulomb and Breit-Coulomb interactions. Retarded electric-dipole matrix elements (in length and velocity forms) are calculated in second order for transitions from excited $3l\ensuremath{-}{4l}^{\ensuremath{'}}$ states to the closed-shell ground state. Wavelengths for 3-4 and 4-4 transitions are compared with experimental data, and with other high-precision calculations. Trends of oscillator strengths as functions of nuclear charge Z are shown graphically for selected transitions.

Excitation energies, transition probabilities, and lifetimes are calculated for 3 l 13l 2-3l 33l 4 electric dipole transitions in Mg-like ions with nuclear charges Z ranging from 13 to 100. Relativistic many-body perturbation theory ~MBPT!, including the Breit interaction, is used to evaluate retarded E1 matrix elements in length and velocity forms. The calculations start from a 1 s 2 2s 2 2p 6 Dirac-Fock potential. First-order perturbation theory is used to obtain intermediate coupling coefficients, and the second-order MBPT is used to determine the matrix elements. The contributions from negative-energy states are included in the second-order E1 matrix elements to achieve agreement between length-form and velocity-form amplitudes. The resulting transition energies and lifetimes are compared with experimental values and with results from other recent calculations.

Energy levels, radiative transition probabilities and autoionization rates for [Kr]4d94fnl (n = 4–9), [Kr]4d95l'nl (n = 5–9) and [Kr]4d96l'nl (n = 6–7) states in Ag-like tungsten (W27 +) are calculated using the relativistic many-body perturbation theory method, the multiconfiguration relativistic Hebrew University Lawrence Livermore Atomic Code and the Hartree–Fock-relativistic method. Branching ratios relative to the first threshold and intensity factors are calculated for satellite lines, and dielectronic recombination (DR) rate coefficients are determined for the singly excited [Kr]4d10nl (n = 4–9) states. The total DR rate coefficient is derived as a function of electron temperature. These atomic data are important in the modelling of N-shell radiation spectra of heavy ions generated in various collision as well as plasma experiments. The tungsten data are particularly important for fusion application.

Transition rates, oscillator strengths and line strengths are calculated for electric-dipole (E1) transitions between even-parity 4s2, 4p2, 4s4d, 4d2, 4p4f and 4f2 states and odd-parity 4s4p, 4s4f, 4p4d and 4d4f states in Zn-like ions with the nuclear charges ranging from Z = 32 to 100. Relativistic many-body perturbation theory (RMBPT), including the Breit interaction, is used to evaluate retarded E1 matrix elements in length and velocity forms. The calculations start from a 1s22s22p63s23p63d10 Dirac–Fock potential. First-order RMBPT is used to obtain intermediate coupling coefficients and second-order RMBPT is used to calculate transition matrix elements. Contributions from negative-energy states are included in the second-order E1 matrix elements to ensure the gauge independence of transition amplitudes. Transition energies used in the calculation of oscillator strengths and transition rates are from second-order RMBPT. Ground state scalar α0(4s2 1S0) polarizabilities are calculated for Zn-like ions from Z = 33 to 100. To evaluate the α0(4s2 1S0) polarizabilities, we calculate RMBPT energies for the odd-parity 4l5l' complex with J = 1 and line strengths between the even-parity 4l4l' complex with J = 0 and the odd-parity 4l5l', 4l6l' complexes with J = 1.

Satellite spectra of H-like ions have been calculated for Z=16–56. New channels of radiative transitions were added in contradictions to previous calculations. Comparison of two results are discussed.

The energies of the levels of the 1s2141′ autoionization states in the range Z=6–54 have been calculated. The calculation was based on the 1/Z perturbation theory allowing for the relativistic effects in the framework of the Breit operator, higher relativistic effects and radiative corrections.

Energies of the 2s3s (1S0, 3S1), 2s3p (1P1, 3PJ), 2s3d (1D2, 3DJ), 2p3s (1P1, 3PJ), 2p3p (1S0, 3S1, 1P1, 1D2, 3PJ, 3DJ) and 2p3d (1P1, 1D2, 1F3, 3PJ, 3DJ, 3FJ) states of Be-like ions with nuclear charges Z = (4, 5,..., 30, 54) are determined to second order in relativistic many-body perturbation theory. Both the Coulomb interaction and the Breit interaction are included. Corrections for the frequency-dependent Breit interaction are taken into account in lowest order; corrections for the Lamb shift are also estimated and included. Comparisons with experiment and with other theoretical calculations are made. For ions with low nuclear charge, we obtain excellent agreement for the term-splitting. Results for the 2p-3d excitation energy of Xe+50 also agree very well with experimental measurements.

Energies of 3l3l′3l″ states of aluminumlike ions with Z=14?100 are evaluated to second order in relativistic many-body perturbation theory starting from a 1s22s22p6 Dirac-Fock potential. Intrinsic three-particle contributions to the energy are included in the present calculation and found to contribute about 10?20 % of the total second-order energy. Corrections for the frequency-dependent Breit interaction and the Lamb shift are included in lowest order. A detailed discussion of contributions to the energy levels is given for aluminumlike germanium (Z=32). Comparisons are made with available experimental data. We obtain excellent agreement for term splitting, even for low-Z ions. These calculations are presented as a theoretical benchmark for comparison with experiment and theory.

Excitation energies for $2l\ensuremath{-}{3l}^{\ensuremath{'}}$ hole-particle states of Ne-like ions are determined to second order in relativistic many-body perturbation theory (MBPT). Reduced matrix elements, line strengths, and transition rates are calculated for electric-dipole $(E1),$ magnetic-quadrupole $(E2),$ magnetic-dipole $(M1),$ and magnetic-quadrupole $(M2)$ transitions in Ne-like ions with nuclear charges ranging from $Z=11$ to 100. The calculations start from a ${1s}^{2}{2s}^{2}{2p}^{6}$ closed-shell Dirac-Fock potential and include second-order Coulomb and Breit-Coulomb interactions. First-order many-body perturbation theory (MBPT) is used to obtain intermediate-coupling coefficients, and second-order MBPT is used to determine the matrix elements. Contributions from negative-energy states are included in the second-order $E1,$ $M1,$ $E2,$ and $M2$ matrix elements. The resulting transition energies are compared with experimental values and with results from other recent calculations. Trends of $E1,$ $E2,$ $M1,$ and $M2$ transition rates as functions of nuclear charge Z are shown graphically for all transitions to the ground state.

The leading Feynman diagrams contributing to the energy of an atom are calculated. Numerical calculations of the energy matrices are carried out for the states of configurations 1s2s2 and 1s2p2 in three-electron atoms and 1s22s2 and 1s22p2 in four-electron atoms. For the case of Fe XXIV the theoretical wavelengths of the transition are compared with experimental data. The numerical calculation shows that the two-photon diagrams with two and three open ends make contributions of the same order of magnitude to the energy of the atom.

Autoionization levels 1s 2s2 2p2, 1s 2p4 and 1s 2s 2p3 of B-like ions were theoretically investigated for Z= 5–100. Calculation was made using perturbation theory over 1/Z. Relativistic corrections were taken into account in limits of Breit operator. Behaviour of radiative transition probabilityA, autoionization rate Γ and level lifetime τ was considered fromZ = 5 up toZ = 100 in detail for configurations 1s 2s2 2p2, 1s 2p4 withJ = 1/2.

The energies of transitions of the type 1 s2 2 s2 2 p3-1 s2 2 s 2 p4-1 s2 2 p5 were computed for isoelectronic sequence of nitrogen. The account was taken of the Hartree-Fock and correlation energies in the first two-three orders of the perturbation theory and the relativistic corrections in terms of Breit operator. The computed values were compared with experimental results for the isoelectronic oxygen series. Sufficiently good agreement of the computed and experimental results for all isoelectronic sequence manifests rather fast convergence in the series of powers of 1/Z. The perturbation theory was employed in computing the transition probabilities of 1 s2 2 s2 2 p3-1 s2 2 s 2 p4-1 s2 2 p5. The data computed may be used in the identification of the coronal solar spectra and the spectra of high-temperature plasma obtained under the laboratory conditions.

The relativistic energies of the 1 s 2 , 1 s 2 s , 1 s 2 p states of ions are calculated using the Gell-Mann and Low formula and a quantum-electrodynamic expression for the S -matrix. Contributions from the first two orders of Feynman diagrams are calculated.

Relativistic wave functions have been used to calculate the probabilities for (1s2s2p)4P5/2-(1s2Kf)2F5/2 autoionization and (ls2s2p)4P5/2-(1s22s)2 S1/2 magnetic quadrupole transition, together with the lifetimes of the (1s2s2p)4P5/2 states, for lithium-type ions with Z from 10 to 60; the results are compared with measurements and with calculations from literature sources.

The excitation energies and the probabilities for the radiative and radiationless decay of the autoionising states belonging to the 2s22p, 2s2p2 and 2p3 configurations have been calculated for three-electron atomic systems on the basis of perturbation theory with respect to inter-electron interaction in a broad range of values of atomic number Z. Using the results of the diagonalisation calculations of the autoionising states of two-electron systems, the authors have obtained estimates of corrections to the autoionisation widths calculated by perturbation theory. The calculations of the radiative transition probabilities for Fe and Ni ions are in good agreement with the 1976 results of Nussbaumer.

The line strengths of 2–2 and 3–3 transitions (2s22p53s–2s22p53p–2s22p53d, 2s2s2p63s–2s2p63p-2s2p63d, 2s22p53l-2s2p63l) have been calculated for the Ne isoelectronic sequence (Z = 14 ÷ 100). The calculation has been carried out in intermediate coupling. Relativistic corrections have been included through the Breit operator. Perturbation theory in 1/Z has been used to account for electronic interactions.

Reports the classification of 220 spectral lines of Ti XIX, V XX, Cr XXI, Mn XXII, Fe XXIII, Co XXIV, Ni XXC, Cu XXVI, Zn XXVII, Ge XXIX and Se XXXI. The transitions identified are 1s22p2-1s22p3s, 1s22p2-1s22p3d, 1s22s2p-1s22s3s, 1s22s2p-1s22s3d, 1s22s2p-1s22p3p and 1s22s2-1s22s3p. These lines were emitted from laser-produced plasmas. Perturbation theory was used to calculate the wavelengths.