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Energies of [Kr]4d94f2, [Kr]4d94f5l, and [Kr]4d95l5l′ states (with l = s, p, d, f) for Ag-like ions with Z = 50–100 are evaluated to second order in relativistic many-body perturbation theory (RMBPT) starting from a Pd-like Dirac–Fock potential ([Kr]4d10). 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 the one- and two-body contributions. Transition rates and line strengths are calculated for the 4d–4f and 4d–5l electric-dipole (E1) transitions in Ag-like ions with nuclear charge Z = 50–100. 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 silverlike tungsten (Z = 74). The transition energies included 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. Additionally, we perform calculations of energies and transition rates for Ag-like W by the Hartree–Fock relativistic method (Cowan code) and the Multiconfiguration Relativistic Hebrew University Lawrence Atomic Code (HULLAC code) to compare with results from the RMBPT code. These atomic data are important in modeling 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.PACS Nos.: 31.15.A–, 31.15.ag, 31.15.am, 31.15.aj

Energies of 1s2l2l′ and 1s3l3l′ states for Li-like ions with Z = 6–100 are evaluated to second order in relativistic many-body perturbation theory. Second-order Coulomb and Breit–Coulomb interactions are included. The calculations start with a Dirac potential and include all possible 1s2l2l′ and 1s3l3l′ configurations. Correction for the frequency dependence of the Breit interaction is taken into account in lowest order. The Lamb-shift correction to the energies is also included in lowest order. A detailed discussion of the various contributions to the energy levels is given for Li-like iron (Z = 26). We found that the three-electron corrections to the energy contribute about 10–20% of the total second-order energy. Comparisons are made with available experimental data and excellent agreement for term splitting is obtained even for low-Z ions. These calculations are presented as a theoretical benchmark for comparison with experiment and theory.PACS Nos.: 32.30.Rj, 32.70.Cs, 31.25.Jf, 31.15.Md

We calculate energy levels, radiative transition probabilities, and autoionization rates for Be-like oxygen (O4+) including 1s2 2lnl' (n = 2–8, l [Formula: see text] n – 1) and 1s23l' nl (n = 3–6, l [Formula: see text] n – 1) states by the multiconfigurational Hartree–Fock method (Cowan code) and the perturbation theory Z-expansion method (MZ code). The state selective dielectronic recombination-rate coefficients to excited states of Be-like oxygen are obtained, which are useful for modeling O V spectral lines in a recombining plasma. Configuration mixing plays an important role for the principal quantum number, n, distribution of the dielectronic recombination-rate coefficients for 2snl (n [Formula: see text] 5) levels at low electron temperature. The orbital angular momentum quantum number, l, distribution of the rate coefficients shows a peak at l = 4. The total dielectronic recombination-rate coefficient is derived as a function of electron temperature. The dielectronic satellite lines are also obtained. PACS Nos.: 34.80Lx, 32.80Dz, 32.30Jc, 31.10+z

M X-rays have been observed from 1–40 keV/u 181Taq+ (q = 45–49) ions colliding with neutral Ar atoms under single collisions. The most dominant X-rays have been found to be due to transitions of 4p–3d and 4f–3d when the projectiles bring 3d-shell vacancies into collisions. Though much weaker, M X-rays also have been observed in collisions with Ta45+ ions that initially have no 3d-shell vacancy and are understood to originate from transitions of the doubly excited states 3d9nln'l' formed through strong electron–electron interactions after single-electron capture. The observed M X-ray spectra have been compared and reproduced nicely with the synthesized spectra. It has been confirmed that transitions of such doubly excited states also contribute to X-rays at the lower energy region observed even for higher charge ions with 3d vacancies. PACS Nos.: 32.30Rj, 32.70Cs, 32.80Rm, 34.70+e

Several peaks have been observed, in the electron energy range up to 20 eV, due to Coster-Kronig electrons from the autoionizing Rydberg states emitted from 2 MeV u-1 Si5+ ions excited through a carbon foil. To obtain a better understanding of these low-energy electron spectra and their production mechanisms, we synthesize the expected electron spectrum which is compared with the observed electron spectrum. Two theoretical methods, namely the perturbation theory of Z-expansion (MZ code) and the multiconfiguration Hartree-Fock method (Cowan code), are used to calculate the necessary Auger electron energies and emission rates. It has been found that the 1s22pnl-1s22s 2S and 1s22s2pnl-1s22s2 1S decays give the most significant contributions to the observed electron spectrum from threshold up to the 20 eV region. The synthetic electron spectra have also been found to reproduce the observed electron spectra quite nicely when the charge distributions of the projectile Si ions after thin carbon foils are taken into account.

Ejected electron spectra from the singlet and triplet states of doubly excited Ne6+**(1s22pnl), Ne6+**(1s23l3l') and Ne6+**(1s23l4l') ions, produced by 80 keV Ne8+(1s2) + He, Ne and Ar collisions, have been measured by means of a zero-degree electron spectroscopy. Only singlet states were observed when the target was He. In contrast, the contribution from the triplet states prevailed in the spectra for the Ne target. For the Ar target, practically no signals were observed in the energy region for the 1s23lnl' states. Two theoretical methods, the perturbation theory (MZ code) and the multi-configurational Hartree-Fock (Cowan code) were used for identification of ejected-electron spectra. Using the (j) string analysis in the extended classical over-barrier model, we discuss the possibility of the participation of inner electrons in the process of double-electron capture by highly charged ion multi-electron target atoms.

Energy levels, radiative transition probabilities and autoionization rates for Be-like Ne (Ne6+) including 1s22pnl (n = 2-9, l n-1) and 1s23l´nl (n = 3-6, l n-1) states are calculated. Two theoretical methods, the perturbation theory Z-expansion (MZ code) method and the multi-configurational Hartree-Fock (Cowan code) method, are used for the calculations. Autoionizing levels above the 1s22s and 1s22p thresholds are considered and their contributions computed. The state-selective dielectronic recombination rate coefficients from Li-like Ne (Ne7+) ions to Be-like Ne (Ne6+) ions for bound states of Ne6+ ions are obtained. Configuration mixing plays an important role for the principal quantum number, n, distribution of the dielectronic recombination rate coefficients for n6 levels. The orbital angular momentum quantum number, l, distribution of the rate coefficients shows a peak around l = 4-5. The rate coefficients for the excited states with higher n are extrapolated using a scaling law. The total dielectronic recombination rate coefficients are derived as a function of electron temperature.

Reduced matrix elements and transition rates are calculated for all magnetic dipole (M1) transitions within 2l2l' configurations and for some 2l3l' - 2l2l' transitions in Be-like ions with nuclear charges ranging from Z = 4 to 100. Many-body perturbation theory (MBPT), including the Breit interaction, is used to evaluate retarded M1 matrix elements. The calculations start with a (1s)2 Dirac-Fock potential and include all possible n = 2 configurations, leading to 4 odd-parity and 6 even-parity states, and some n = 3 configurations. First-order perturbation theory is used to obtain intermediate coupling coefficients. Second-order MBPT is used to determine the matrix elements, which are evaluated for all 11 M1 transitions within 2l2l' configurations and for 35 M1 transitions between 2l3l' and 2l2l' states. The transition energies used in the calculation of oscillator strengths and transition rates are obtained from second-order MBPT. The importance of negative-energy contributions to M1 transition amplitudes is discussed.

Energy levels and autoionizing rates of 2lnl' (n = 3–12, l = 0–4) configurations for He-like ions with Z = 4–54 were calculated by using the Z expansion method. Relativistic effects are taken into account using the Breit–Pauli operators. The asymptotic dependence on n of the energy matrix is discussed for 2lnl' states. Intermediate coupling coefficients obtained after diagonalizing the energy matrices were also studied. It was observed that these coefficients change very rapidly with n and Z due to a redistribution of contribution between relativistic and correlation effects. As a result, all other atomic characteristics (radiative and nonradiative transition probabilities, branching ratios) display non-monotonous Z- and n-dependences with maxima and minima.

Ejected electrons from the singlet and triplet states of doubly excited and ions, produced by 25, 50, 75 and 100 keV and Ar collisions have been measured with high-resolution electron spectroscopy. Only singlet states were observed when the target was He; in contrast, many triplet states were observed in and Ar collisions. Both singlet and triplet states contributed to the electron spectra in collisions, in particular, triplet states were conspicuous at low energy. Two theoretical methods, perturbation theory or Z expansion (MZ code) and multiconfigurational Hartree-Fock (Cowan code) were used for identification of ejected-electron spectra. The collision energy dependence of the spectra is discussed.

The dielectronic recombination rate coefficients to the excited states for n = 2-6 are calculated including - states. The values for the excited states higher than n = 6 are extrapolated and the total dielectronic recombination rate coefficients are derived.

The excitation energies and the probabilities for radiative and radiationless decays of hollow atom states belonging to the 2s22p, 2s2p2 and 2p3 configurations have been calculated on the basis of perturbation theory method (1/Z-expansion) in a broad range of values of atomic number Z. Our results agree well with the first observation of these states and the theoretical and experimental results obtained recently for neutral Li atoms. It should be noted that the 1/Z expansion method gives more accurate results for ions than for neutral systems, because of the limited number of coefficients of 1/Z expansion calculated in this work. In this case the good agreement provided by our results for neutral system allows us to believe that our data for the same triply excited states with Z>3 should be used for prediction of new experiments with these states.

Energy levels, radiative transition probabilities and autoionization rates for CuXIX including the 1s22s22p53lnl' (n = 3 ÷ 8, l' ≤ n – 1) and 1s22s2p63lnl' (n = 3 ÷ 4, l' ≤ n – 1) doubly excited states were calculated using the multi-configurational Hartree–Fock method (Cowan code). Contributions of relativistic effects were discussed in comparison with data obtained by the multi-configurational Dirac–Fock method (YODA code). Application of the theoretical data for interpretation of experimental spectra obtained by double-electron capture in slow ion-atom collisions is discussed.

Single and double electron capture processes by O 6+ from He at 90 keV have been investigated by observation of the emission spectrum in the wavelength region of 290–510 nm. In addition to transitions from excited states of O 5+ populated by single electron capture processes, Yrast transitions from Rydberg states (1s 2 2s n l ) of O 4+ populated by double electron capture have been observed. Transfer target excitation processes have been confirmed by the observation of transitions from excited states of He + .

Energies of the low-lying excited states of six atomic systems with two electrons above the core (Mg I, Al II, Hg I, Tl II, Pb I, and Bi II) and three systems with three electrons above the core (Al I, Tl I, and Bi I) are determined to second order in relativistic many-body perturbation theory using frozen-core Dirac-Hartree-Fock orbitals as a basis set. In the present report, the Breit interaction is included to first order only. Diagonalization of the effective Hamiltonian is carried out using two methods: (I) the symmetric first-order Hamiltonian (including both Coulomb and Breit interactions) is diagonalized and then the second-order correlation is determined using the first-order eigenvectors; (II) the first-order (Coulomb plus Breit) together with the non-symmetric second-order effective Hamiltonian is diagonalized. Different model spaces are considered. Contributions from the three-electron interaction are compared with contributions from the two- and one-electron interactions. Comparisons with experiment are made.

Energy levels, radiative transition probabilities and autoionization rates for CIII including 1s22pnl′ [n = 2–6, l′ ≤ (n − 1)] and 1s23lnl′ [n = 3–6, l′ ≤ (n − 1)] states were calculated by using the multi-configurational Hartree-Fock method (Cowan code). Autoionizing levels above the 1s22s and 1s22p thresholds were considered and their contributions were computed. Branching ratios on the autoionization rate to the first threshold and intensity factors were calculated for satellite lines of the CIII ion. The dielectronic recombination rate coefficients to the excited states for n = 2–6 were calculated. The values for the excited states higher than n = 6 were extrapolated and the total dielectronic recombination rate coefficients were derived. The rate coefficients to the excited states were fitted to an analytical formula and the fit parameters are given.

The dielectronic recombination rate coefficients to the excited states for n = 2–6 are calculated including 1s22l2l'nl'' (n = 2–6, l'' ≤ (n − 1)). The values for the excited states higher than n = 6 are extrapolated and the total dielectronic recombination rate coefficients are derived. The rate coefficients to the excited states are fitted to an analytical formula and the fit parameters are given. The effective recombination rate coefficient for different electron densities are also derived.

Atomic properties of the 24 low-lying $ns$, $n{p}_{j}$, $n{d}_{j}$, $n{f}_{j}$, and $n{g}_{j}$ states in Th$\phantom{\rule{0.16em}{0ex}}$iv ion are calculated using the high-precision relativistic all-order method where all single, double, and partial triple excitations of the Dirac-Fock wave functions are included to all orders of perturbation theory. Recommended values are provided for a large number of electric-dipole matrix elements, oscillator strengths, transition rates, and lifetimes. Scalar polarizabilities of the ground and six excited states ($5{f}_{j}$, $6{d}_{j}$, $7{p}_{j}$, and $7s$), and tensor polarizabilities of the $5{f}_{j}$, $6{d}_{j}$, and $7{p}_{3/2}$ states of Th$\phantom{\rule{0.16em}{0ex}}$iv are evaluated. The uncertainties of the recommended values are estimated. These calculations provide recommended values critically evaluated for their accuracy for a number of Th$\phantom{\rule{0.16em}{0ex}}$iv atomic properties for use in theoretical modeling as well as planning and analysis of various experiments including development of an ultraprecise nuclear clock and resonant excitation Stark ionization spectroscopy studies of actinide ions.

Ejected electrons from the doublet and quartet states of doubly excited ions, produced by 60 keV collisions have been measured with high resolution zero-degree electron spectroscopy. Only the doublet states were observed in collisions with gas. Both doublet and quartet states were observed when was used as the target. Two theoretical methods, perturbation theory or Z-expansion (MZ code) and multi-configurational Hartree - Fock (Cowan code) were used for identification of peaks observed in ejected-electron spectra. Contributions of correlation effects are discussed by comparison with other theoretical energies.

Energy levels, radiative transition probabilities and autionization rates for C II including 1s22l2l'nl" (n = 2–6, l" ≤ (n − 1)] states were calculated by using the multi-configurational Hartree-Fock (Cowan code) method. Autoionizing levels above three thresholds: 1s22s2(1S), 1s22s2p(3P), 1s22s2p(1P) were considered. Branching ratios relative to the first threshold and intensity factors were calculated for satellite lines and dielectronic recombination rate coefficients for C II ions.

Ejected electrons from the singlet and triplet states of doubly excited O4+ (1s23l3l') and O4+ (1s23l4l') ions, produced by 60 and 120 keV O6+ (1s2) 1S+X collisions (X identical to He, Ne, Ar), have been measured with high resolution zero-degree electron spectroscopy. Only the singlet states were observed when He gas was the target. In contrast, mainly triplet states were observed when Ne gas was used. Both singlet and triplet states contributed to the electron spectra, produced by O6+ (1s2) 1S+Ar collisions. Two theoretical methods, perturbation theory or Z-expansion (MZ code) and multiconfigurational Hartree-Fock (Cowan code) were used for identification of ejected-electron spectra. The contribution of correlation effects is discussed by comparison with other theoretical energies.

Wavelengths, line strengths, and transition rates are calculated for the multipole ($E1$, $M1$, $E2$, $M2$, $E3$, and $M3$) transitions between the excited $6{s}^{2}6{p}^{5}nl$ and $6s6{p}^{6}nl$ states and the ground $6{s}^{2}6{p}^{6}$ state in Ac${}^{3+}$, Th${}^{4+}$, and U${}^{6+}$ Rn-like ions. Relativistic many-body perturbation theory (RMBPT), including the Breit interaction, is used to evaluate energies and transition rates for multipole transitions in these hole-particle systems. The RMBPT method agrees with multiconfigurational Dirac-Fock (MCDF) calculations in lowest order, includes all second-order correlation corrections, and includes corrections from negative-energy states. The calculations start from a [Xe]$4{f}^{14}5{d}^{10}6{s}^{2}6{p}^{6}$ Dirac-Fock potential. First-order perturbation theory is used to obtain intermediate-coupling coefficients, and second-order RMBPT is used to determine the matrix elements. Evaluated multipole matrix elements for transitions from excited states to the ground states are used to determine the line strengths, transition rates, and multipole polarizabilities. This work provides a number of yet unmeasured properties of these actinide ions for various applications and for benchmark tests of theory and experiment.

The operation of atomic clocks is generally carried out at room temperature, whereas the definition of the second refers to the clock transition in an atom at absolute zero. This implies that the clock transition frequency should be corrected in practice for the effect of finite temperature, of which the leading contributor is the blackbody radiation (BBR) shift. Experimental measurements of the BBR shifts are difficult. In this work, we have calculated the blackbody radiation shift of the ground-state hyperfine microwave transition in {sup 87}Rb using the relativistic all-order method and carried out a detailed evaluation of the accuracy of our final value. Particular care is taken to accurately account for the contributions from highly excited states. Our predicted value for the Stark coefficient, k{sub S}=-1.240(4)x10{sup -10} Hz/(V/m){sup 2}, is three times more accurate than the previous calculation [E. J. Angstman, V. A. Dzuba, and V. V. Flambaum, Phys. Rev. A 74, 023405 (2006)].

Excitation energies of the $[\mathrm{Kr}]{\mathit{ns}}_{1/2}$, $[\mathrm{Kr}]{\mathit{np}}_{j}$, $[\mathrm{Kr}]{\mathit{nd}}_{j}$, and $[\mathrm{Kr}]{\mathit{nf}}_{j}$ ($n\ensuremath{\leqslant}9$ and $[\mathrm{Kr}]=(1{s}^{2}2{s}^{2}2{p}^{6}3{s}^{2}3{p}^{6}3{d}^{10}4{s}^{2}4{p}^{6}$) in Sr ii are evaluated. First-order, second-order, third-order, and all-order Coulomb energies and first-order and second-order Coulomb-Breit energies are calculated. Reduced matrix elements, oscillator strengths, transition rates, and lifetimes are determined for the levels up to $n=7$. Electric-dipole ($5{s}_{1/2}\ensuremath{-}{\mathit{np}}_{j}$, $n=5--26$), electric-quadrupole ($5{s}_{1/2}\ensuremath{-}{\mathit{nd}}_{j}$, $n=4--26$), and electric-octupole ($5{s}_{1/2}\ensuremath{-}{\mathit{nf}}_{j}$, $n=4--26$) matrix elements are calculated to obtain the ground-state $E1$, $E2$, and $E3$ static polarizabilities. Scalar and tensor polarizabilities for the $5{p}_{j}\ensuremath{-}9{p}_{j}$ and $4{d}_{j}\ensuremath{-}8{d}_{j}$ excited states in Sr ii are also calculated. All the above-mentioned matrix elements are determined using the all-order method. We also investigate the hyperfine structure in $^{87}\mathrm{Sr}$${}^{+}$. The hyperfine $A$ values and $B$ values are determined for the first low-lying levels up to $n=7$. The quadratic Stark effect on hyperfine-structure levels of the $^{87}\mathrm{Sr}$${}^{+}$ ground state is investigated. The calculated shift for the $(F=5,M=0)\ensuremath{\leftrightarrow}(F=4,M=0)$ transition is found to be 0.120(1) Hz/(kV/cm)${}^{2}$. These calculations provide a theoretical benchmark for comparison with the experiment and theory. A careful study of uncertainty of our calculations is carried out for the transition-matrix elements, line strengths, transition rates, lifetimes, polarizabilities, and the Stark shift coefficient.

Excitation energies of the [Xe]${\mathit{ns}}_{1/2}$, [Xe]${\mathit{np}}_{j}$, and [Xe]${\mathit{nd}}_{j}$ ($n\ensuremath{\leqslant}$ $12$ and $[\mathrm{Xe}]=1{s}^{2}2{s}^{2}2{p}^{6}3{s}^{2}3{p}^{6}3{d}^{10}4{s}^{2}4{p}^{6}4{d}^{10}5{s}^{2}5{p}^{6}$) in Ba ii are evaluated. First-, second-, third-, and all-order Coulomb energies and first- and second-order Coulomb-Breit energies are calculated. Electric-dipole ($6{s}_{1/2}$-${\mathit{np}}_{j}$, $n=6$--26), electric-quadrupole ($6{s}_{1/2}$-${\mathit{nd}}_{j}$, $n=5$--$26$), and electric-octupole ($6{s}_{1/2}$-${\mathit{nf}}_{j}$, $n=4$--$26$) matrix elements are calculated to obtain the ground-state $E1$, $E2$, and $E3$ static polarizabilities. Scalar polarizabilities of the ${\mathit{ns}}_{1/2}$, ${\mathit{np}}_{j}$, and ${\mathit{nd}}_{j}$ states and tensor polarizabilities of the ${\mathit{np}}_{3/2}$ and ${\mathit{nd}}_{j}$ excited states of Ba${}^{+}$ are evaluated. All aforementioned matrix elements are determined using the relativistic all-order method. The hyperfine structure in $^{137}\mathrm{Ba}$ ii is also investigated. The hyperfine $A$ and $B$ values are determined for the first low-lying levels up to $n=9$. The quadratic Stark effect on hyperfine structure levels of $^{137}\mathrm{Ba}$ ii ground state is investigated. The calculated shift for the ($F=2$, $M=0$) $\ensuremath{\leftrightarrow}$ ($F=1$, $M=0$) transition is $\ensuremath{-}$$0.2931$ Hz/(kV/cm)${}^{2}$, in agreement with a previous theoretical result, $\ensuremath{-}0.284(3)$). These calculations provide a theoretical benchmark for comparison with experiment and theory.

Three different calculational methods (AUTOLSJ, MZ, MCDF) are used to obtain energy levels and autoionization rates for doubly-excited states 2141′ of two electron systems (10⩽ Z ⩽42). By ordering all the states by energy within each block of a given angular momentum J and parity, it becomes possible to compare energy levels and autoionization rates obtained by the three methods. The Z dependences of the quantities are investigated for each calculational method for 10⩽ Z ⩽42. The final comparison reveals rather good agreement between the results obtained by the three methods.

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.

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

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

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.

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.

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.

Branching ratios between the radiative single- and double-electron transitions into the doubly ionized K shell have been calculated in lowest order perturbation theory as a function of the atomic number. The results obtained are compared with the calculations of other authors and with the available experimental data.

Measurements and calculations of 3-2 transitions in Ne-like highly charged ions were performed. The measurements have been carried out for ions with nuclear charge Z = 39-60 excited in a low-inductance vacuum spark plasma. The Z-expansion and two versions of model potential methods were used in our calculations for all ions with Z = 36-92. A comparison of all available theoretical and experimental data for these transitions were made (Z ≥ 38). Recommended wavelengths which can be useful for identification of 3-2 spectra of Ne-like ions are given.

An analysis was made of the intensities of satellites of the La resonance doublet of H-like ions with nuclear charges in the range Z = 12–16, corresponding to transitions from autoionizing doubly excited levels of He-like ions. Consideration of transitions of the ls2l'–2l2l' and 1s3l'–2l3l' types made it possible to integrate completely the spectrum of a laser plasma formed when the power density of the heating radiation was q ~ 1014 W/cm2. The agreement between the theory and experiment was good, with the exception of the intensity of the λ = 8.5305A line in the Mg spectrum.

An analysis was made of the distribution of the relative intensities of spectral lines with a common upper level in transitions of the 2s2pk+1–2pk+2 type in N-, C-, B-, and Be-like ions of Ca, Ti, and Fe excited in a laser plasma and recorded photographically by a glancing-incidence spectrograph. Use was made of theoretically calculated transition probabilities. The relative spectral sensitivity of a DFS-6 spectrograph used in combination with UF-4 photographic emulsions was determined as a function of the wavelength in the range 100–250 A. It was found that the dependence is nonmonotonic. The results were used in some diagnostic applications to laser plasma spectra.

The first few terms of the perturbation expansions for the function and the energy shift of a degenerate state of an arbitrary quantum mechanical system are obtained using the adiabatic formula. It is shown how the expansion for the secular operator may be obtained from the expansion for the function. The results are used to calculate energies of the ground and some excited states and multiplet splittings of some beryllium-like ions.

'Itto different calculational methods (AUTOLSJ and MZ) are used to obtain the energy levels and autoionization probabilities for doubly excited states 29. 3i' of two-electron systems. A Z dependence of these parameters for an isoelectronic sequmce of He-like ions (6 < Z < 44) and a comparison between the results obtained by these two methods are presented.

The possibility of stimulated emission as a result of transitions in multiply charged neon-like ions is considered. The energies of excited terms with the 2p53s, 2p53p, and 2p53d configurations are calculated for ions with Z=4–17. The wavelengths of the expected laser transitions are given for the λ≈250–1600 A range.

Wholly relativistic calculations of the transition probabilities in two-electron ions with arbitrary high nuclear charge Z are made. The Dirac one-electron functions and the exact electromagnetic interaction operator are used. All the transitions between the levels of the ground (1s)2 and excited 1s2s+1s2p configurations are calculated.

We have previously [1] calculated diagram contributions for the f i r s t two orders of per turbat ion theory for the ground states and cer ta in excited states of light atoms. We have also given [2] numer ica l values for the contribution from d iagrams for s ta tes with fil led shells 1 and 2 together with one e lectron or one hole in shell n = 3. Here we consider s tates with two e lec t rons (holes) in shell n = 3.

The contributions from the diagrams of the first two orders are calculated for the energy of the ground state of Be. The result is E2= =−1.25 Z2+1.55927422 Z−0.8775, with E 2 corr =−0.01172683 Z −0.0720. Perturbation theories for the ground-state energy of Be are compared for Hartree-Fock and hydrogen-type functions.