Allowed and forbidden transition parameters for Fe XV

A comprehensive set of fine structure energy levels, oscillator strengths (f), line strengths (S), and radiative decay rates (A) for bound-bound transitions in Fe XV is presented. The allowed electric dipole (E1) transitions were obtained from the relativistic Breit-Pauli R-matrix method which is based on the close coupling approximation. A total of 507 fine structure energy levels with n ? 10, l ? 9, and 0 ? J ? 10 are found. They agree within 1% with the available observed energies. These energy levels yield a total of 27,812 E1, same-spin multiplets and intercombination transitions. The A values are in good agreement with those compiled by NIST and other existing values for most transitions. Forbidden transitions are obtained from a set of 20 configurations with orbitals ranging from 1s to 5f using the relativistic code SUPERSTRUCTURE (SS) in the Breit-Pauli approximation. From a set of 123 fine structure levels, a total of 6962 S and A values are presented for forbidden electric quadrupole (E2), electric octupole (E3), magnetic dipole (M1), and magnetic quadrupole (M2) transitions. The energies from SS calculations agree with observed energies to within 1-3%. A values for E2, M1 transitions agree very well with the available values for most transitions while those for M2 transitions show variable agreement. The large set of transition parameters presented should be applicable for both diagnostics and spectral modeling in the X-ray, ultraviolet, and optical regions of astrophysical plasmas.     

Oscillator strengths and transition probabilities of O II

The abundance of singly ionized oxygen, O II, in planetary nebulae provides crucial diagnostic tests for the physical conditions present in these astrophysical environments. The abundance can be determined from the absorption lines formed by the radiative processes, such as the photo-excitations reported here. Radiative transitions are obtained from a total of 708 fine structure levels of O II with , and 1/2?J?17/2. For spectral analysis oscillator strengths, line strengths, and transition probabilities (A) are presented for 51,733 electric dipole fine structure radiative transitions. The calculations were carried out in the relativistic Breit-Pauli R-matrix approximation. The transitions have been identified spectroscopically using quantum defect analysis and other criteria. The calculated energies agree with the observed energies within 5% for most of the levels. However, some relatively large differences are noted, the largest difference being 13% for the level 2s²2p²(¹D)4p(²F^o)_7/2. Most of the A values and lifetimes agree with the existing measured and calculated values. The transitions should be applicable for diagnostics as well as spectral modeling in the ultraviolet and optical regions of astrophysical and laboratory plasmas.     

Revised transition probabilities for Fe XXV: Relativistic CI calculations

Revised data are provided for transition probabilities between fine-structure components of levels with n ? 6 in Fe XXV. Earlier published data for transitions between fine-structure levels in Fe XXV are found to be in error, especially for certain classes of transitions. The purpose of the present note is to provide a corrected database for transitions in Fe XXV. Wavefunctions and energies for states with n ? 6 and J = 0, 1, 2, 3 are determined using a relativistic configuration interaction (CI) expansion that includes the Breit interaction. To measure and control the numerical accuracy of the calculations, we compare our CI energies and matrix elements with values calculated using relativistic second-order many-body perturbation theory (MBPT), also including the Breit interaction. We obtain good agreement between our CI and MBPT calculations but disagree with earlier calculations for transitions with ΔL = 2 and for intercombination transitions (ΔS = 1). We provide wavelengths, line strengths, and transitions rates for fine-structure transition between levels with n ? 6 in Fe XXV.     

Relativistic energy levels, lifetimes, and transition probabilities for the sodium-like to argon-like sequences

Energy levels, lifetimes, and transition probabilities for transitions between computed levels are reported for the Na-like (Z = 11, … , 26) to Ar-like (Z = 18, … , 30) sequences. Several methods have been used—non-orthogonal spline CI, multiconfiguration Hartree-Fock (MCHF), and also multiconfiguration Dirac-Hartree-Fock (MCDHF). The first two methods included relativistic effects through the Breit-Pauli Hamiltonian, omitting only the orbit-orbit interaction. Both allowed (E1) and some forbidden (M1, E2, M2, E3) transitions are reported.     

Fluorescence yields and Coster-Kronig probabilities for the atomic L subshells. Part II: The L1 subshell revisited

Our recently recommended values for the L1 subshell fluorescence yield ω₁ and Coster-Kronig probabilities f₁₃ and f₁₂ in the atomic number range 64 ? Z ? 92 are re-assessed in the light of new experimental data. Special attention is paid to the regions of atomic number in which discontinuities arise due to the onset of L1L2N1, L1L3M4, and L1L3M5 transitions. Attention is drawn to large scatter and to systematic differences in the data from different experimental techniques, both of which result in large uncertainties being attached to the recommended values. The urgent need for additional refined measurements is emphasized.     

Mi (i = 1-5) subshell fluorescence and Coster-Kronig yields for elements with 67 ? Z ? 92

A complete set of the M_i (i = 1-5) subshell fluorescence and Coster-Kronig (CK) yields has been generated by interpolation for elements with 67 ? Z ? 92 from the Dirac-Hartree-Slater (DHS) model based values tabulated for a limited number of elements, considering the cutoff/onset of different CK transitions in accordance with the CK transition energies evaluated in the present work. The CK transition energies have been deduced from tabulated values of the Dirac-Hartree-Fock-Slater model based neutral atom binding energies [K. Huang, M. Aoyagi, M.H. Chen, B. Crasemann, H. Mark, At. Data Nucl. Data Tables 18 (1976) 243] and the L_i (i = 1-3) subshell CK transition energies [M.H. Chen, B. Crasemann, K. Huang, M. Aoyagi, H. Mark, At. Data Nucl. Data Tables 19 (1977) 97] in order to establish the cutoff/onset of different CK transitions at specific atomic numbers. A second set of the M_i (i = 1-5) subshell fluorescence yields have also been deduced using radiative widths computed from the Dirac-Fock (DF) model based X-ray emission rates, and the total widths reevaluated to incorporate the DF model based radiative widths in place of those based on the DHS model. Further, the CK-corrected (ν_i) and average fluorescence (?_M) fields, which are experimentally important, have been evaluated from the generated set of CK yields and two sets of fluorescence yields.     

Relativistic energy, fine structure, and hyperfine-structure studies of the high-lying core-excited states P(n) (n = 1-3) and S(m) (m = 1-3) for the Be-like isoelectronic sequence

The variational method using a multiconfiguration interaction wavefunction is carried out on the high-lying core-excited states ⁵P(n) (n = 1-3) and ⁵S^o(m) (m = 1-3) for the Be-like isoelectronic sequence from Z = 7 to 10, including mass polarization and relativistic corrections. Relativistic energies, oscillator strengths, wavelengths, and lifetimes are reported. The results are compared with other theoretical and experimental data in the literature. The fine structure and hyperfine structure of core-excited states for this system are also investigated.     

Oscillator strengths and transition probabilities for allowed and forbidden transitions in Fe XIX

An extensive set of oscillator strengths, line strengths, and radiative decay rates for the allowed and forbidden transitions in Fe XIX is presented. They correspond to 1626 fine structure levels of total angular momenta 0≤J≤8 of even and odd parities with 2≤n≤10, 0≤l≤9, 0≤L≤10, and (2S+1)=1, 3, 5. In contrast, the compiled table of the National Institute for Standards and Technology (NIST) lists only 63 observed levels. A total of 289,291 electric dipole allowed transitions are presented. They were obtained in the close coupling approximation using the relativistic Breit-Pauli R-matrix method. The wavefunction expansion included 15 levels of the configurations 2s²2p³, 2s2p⁴, and 2p⁵ of the Fe XX core. The calculated fine structure levels are assigned with spectroscopic identifications using quantum defect analysis. Comparison with the observed energies shows very good agreement, the largest difference being less than 4%. The transitions also compare well with the compiled data by NIST and recent calculations. The forbidden transitions of the electric quadrupole and octupole, and magnetic dipole and quadrupole, type are presented for the 379 levels of the configurations 2s²2p⁴, 2s2p⁵, 2p⁶, 2s²2p³3s, 2s²2p³3p, 2s²2p³3d, 2s²2p³4s, 2s²2p³4p, 2s²2p³4d, 2s²2p³4f, 2s2p⁴3s, 2s2p⁴3p, 2s2p⁴3d, 2s2p⁴4s, 2s2p⁴4p, and 2s²2p²3s² of Fe XIX. They correspond to a total of 66,619 transitions. These results have been obtained from relativistic Breit-Pauli atomic structure calculations using the program SUPERSTRUCTURE. The forbidden transition probabilities show very good agreement with those compiled by NIST.     

Internal conversion coefficients of high multipole transitions: Experiment and theories

A compilation of the available experimental internal conversion coefficients (ICCs), α_T, α_K, α_L, and ratios K/L and K/LM of high multipole (L > 2) transitions for a number of elements in the range 21 ? Z ? 94 is presented. Our listing of experimental data includes 194 data sets on 110 E3 transitions, 10 data sets on 6 E4 transitions, 11 data sets on 7 E5 transitions, 38 data sets on 21 M3 transitions, and 132 data sets on 68 M4 transitions. Data with less than 10% experimental uncertainty have been selected for comparison with the theoretical values of Hager and Seltzer [R.S. Hager, E.C. Seltzer, Nucl. Data Tables A 4 (1968) 1], Rosel et al. [F. Rösel, H.M. Fries, K. Alder, H.C. Pauli, At. Data Nucl. Data Tables 21 (1978) 91], and BRICC. The relative percentage deviations (%Δ) have been calculated for each of the above theories and the averages are estimated. The Band et al. [I.M. Band, M.B. Trzhaskovskaya, C.W. Nestor Jr., P.O. Tikkanen, S. Raman, At. Data Nucl. Data Tables 81 (2002) 1] tables, using the BRICC interpolation code, are seen to give theoretical ICCs closest to experimental values.     

Oscillator strengths and transition probabilities from the Breit–Pauli R-matrix method: Ne IV

The atomic parameters–oscillator strengths, line strengths, radiative decay rates (A$A$), and lifetimes–for fine structure transitions of electric dipole (E1) type for the astrophysically abundant ion Ne IV are presented. The results include 868 fine structure levels with n≤$n\le$ 10, l≤$l\le$ 9, and 1/2≤J≤$\le J\le$ 19/2 of even and odd parities, and the corresponding 83,767 E1 transitions. The calculations were carried out using the relativistic Breit–Pauli R-matrix method in the close coupling approximation. The transitions have been identified spectroscopically using an algorithm based on quantum defect analysis and other criteria. The calculated energies agree with the 103 observed and identified energies to within 3% or better for most of the levels. Some larger differences are also noted. The A$A$-values show good to fair agreement with the very limited number of available transitions in the table compiled by NIST, but show very good agreement with the latest published multi-configuration Hartree–Fock calculations. The present transitions should be useful for diagnostics as well as for precise and complete spectral modeling in the soft X-ray to infra-red regions of astrophysical and laboratory plasmas.     

Measurement of transformation temperatures and specific heat capacity of tungsten added reduced activation ferritic-martensitic steel

The on-heating phase transformation temperatures up to the melting regime and the specific heat capacity of a reduced activation ferritic-martensitic steel (RAFM) with a nominal composition (wt%): 9Cr-0.09C-0.56Mn-0.23V-1W-0.063Ta-0.02N, have been measured using high temperature differential scanning calorimetry. The α-ferrite + carbides → γ-austenite transformation start and finish temperatures, namely Ac₁, and Ac₃, are found to be 1104 and 1144 K, respectively for a typical normalized and tempered microstructure. It is also observed that the martensite start (M_S) and finish (M_f) temperatures are sensitive to the austenitising conditions. Typical M_S and M_f values for the 1273 K normalized and 1033 K tempered samples are of the order 714 and 614 K, respectively. The heat capacity C_P of the RAFM steel has been measured in the temperature range 473-1273 K, for different normalized and tempered samples. In essence, it is found that the C_P of the fully martensitic microstructure is found to be lower than that of its tempered counterpart, and this difference begins to increase in an appreciable manner from about 800 K. The heat capacity of the normalized microstructure is found to vary from 480 to 500 J kg⁻¹ K⁻¹ at 500 K, where as that of the tempered steel is found to be higher by about, 150 J kg⁻¹ K⁻¹.     

Microstructure evolution of Ge implanted silicon oxide thin films upon annealing treatments

The structural evolution of silicon oxide films with Ge⁺ implantation was traced with a positron beam equipped with positron annihilation Doppler broadening and lifetime spectrometers. Results indicate that the film structure change as a function of the annealing temperature could be divided into four stages: (I) T < 300 °C; (II) 300 °C ? T ? 500 °C; (III) 600 °C ? T ? 800 °C; (IV) T ? 900 °C. In comparison with stage I, the increased positron annihilation Doppler broadening S values during stage II is ascribed to the annealing out of point defects and coalescence of intrinsic open volumes in silicon oxides. The obtained long positron lifetime and high S values without much fluctuation in stage III suggest a rather stable film structure. Further annealing above 900 °C brings about dramatic change of the film structure with Ge precipitation. Positron annihilation spectroscopy is thereby a sensitive probe for the diagnosis of microstructure variation of silicon oxide thin films with nano-precipitation.     

Electron impact collision strengths in Si IX, Si X, and Si XI

Electron impact collision strengths among 560 levels of Si IX, 320 levels of Si X, and 350 levels of Si XI have been calculated using the Flexible Atomic Code of Gu [M.F. Gu, Astrophys. J. 582 (2003) 1241]. Collision strengths Ω at 10 scattered electron energies, namely 10, 50, 100, 200, 400, 600, 800, 1000, 1500, and 2000 eV, are reported. Assuming a Maxwellian energy distribution, effective collision strengths ? are obtained on a finer electron temperature grid of 0.5, 1.0, 2.0, 3.0, 4.0, 5.0, and 6.0 MK, which covers the typical temperature range of astrophysical hot plasmas. Additionally, radiative rates A and weighted oscillator strengths gf are given for the more probable transitions among these levels. Comparisons of our results with available predictions reported in earlier literature are made and the accuracy of the data is assessed. Most transitions exhibit a good agreement, but large differences in gf appear for a few cases, which are due to the different configuration interactions included in different theoretical calculations. For excitations among levels of the ground and lower excited configurations, large discrepancies of ? may have resulted from the consideration of resonance effects in earlier works.     

Relativistic multireference Møller-Plesset perturbation theory calculations of the energy levels and transition probabilities in Ne-like xenon, tungsten, and uranium ions

Relativistic multireference many-body Møller-Plesset perturbation theory (MR-MP) calculations have been performed on neonlike xenon, tungsten, and uranium ions. The 2s⁻¹n? and 2p⁻¹n? (n ? 5, ? ? 4) energy levels, lifetimes and transition probabilities are reported. The second-order MR-MP calculation of energy levels included mass shifts, frequency-dependent first-order Breit correction and Lamb shifts. The calculated transition energies are compared with other theoretical and experimental data. The synthetic radiative spectra is presented for different wavelength regions.     

Energies and E1, M1, E2, and M2 transition rates for states of the 2s2p, 2s2p,and 2p configurations in nitrogen-like ions between F III and Kr XXX

Based on relativistic wavefunctions from multiconfiguration Dirac–Hartree–Fock and configuration interaction calculations, E1, M1, E2, and M2 transition rates, weighted oscillator strengths, and lifetimes are evaluated for the states of the (1s²)2s²2p³,2s2p⁴, and 2p⁵ configurations in all nitrogen-like ions between F  III and Kr  XXX. The wavefunction expansions include valence, core–valence, and core–core correlation effects through single–double multireference expansions to increasing sets of active orbitals. The computed energies agree very well with experimental values, with differences of only 300–600 cm⁻¹ for the majority of the levels and ions in the sequence. Computed transitions rates are in close agreement with available data from MCHF-BP calculations by Tachiev and Froese Fischer [G.I. Tachiev, C. Froese Fischer, A&A 385 (2002) 716].     

Semi-empirical predictions of even atomic energy levels and their hyperfine structure for the scandium atom

We report fine and hyperfine structure analysis of the system of even configurations of the Sc atom in a large multi-configuration basis. The complete energy scheme in the energy region up to about 50,000 cm⁻¹ has been established with the predicted values of the hyperfine structure constants A. The effects of the configuration interaction in the fine and hyperfine structure are discussed.     

Alkali ion scattering from Ag(0 0 1) and Ag thin films at low and hyperthermal energies

We have investigated the scattering of K⁺ and Cs⁺ ions from a single crystal Ag(0 0 1) surface and from a Ag-Si(1 0 0) Schottky diode structure. For the K⁺ ions, incident energies of 25 eV to 1 keV were used to obtain energy-resolved spectra of scattered ions at θ_i = θ_f = 45°. These results are compared to the classical trajectory simulation safari and show features indicative of light atom-surface scattering where sequential binary collisions can describe the observed energy loss spectra. Energy-resolved spectra obtained for Cs⁺ ions at incident energies of 75 eV and 200 eV also show features consistent with binary collisions. However, for this heavy atom-surface scattering system, the dominant trajectory type involves at least two surface atoms, as large angular deflections are not classically allowed for any single scattering event. In addition, a significant deviation from the classical double-collision prediction is observed for incident energies around 100 eV, and molecular dynamics studies are proposed to investigate the role of collective lattice effects. Data are also presented for the scattering of K⁺ ions from a Schottky diode structure, which is a prototype device for the development of active targets to probe energy loss at a surface.     

Breit-Pauli energy levels belonging to 2p, 2s2p, 2p, 2p3? configurations and all E1 transitions among these levels in Mg V

We present accurate oscillator strengths, line strengths and radiative rates for 1073 E1 transitions among the 86 levels belonging to 2s²2p⁴, 2s2p⁵, 2p⁶, and 2s²2p³(⁴S^o, ²D^o, ²P^o)3? configurations in Mg V. We have used 1s and 2s Hartree-Fock orbitals, re-optimized 2p on 2p³(²D^o)3s ³D^o and optimized 3s,3p,3d orbitals on real states. Sixteen additional orbitals up to 8d are optimized either as a correction to n = 3 physical orbitals or as a correlation orbital. A very large set of configurations including up to three electron promotions are used to account for all important correlation effects. All of the main five terms in the Breit-Pauli operator (except the orbit-orbit interaction) are included in order to account for the relativistic effects. Small adjustments to the diagonal elements of the Hamiltonian matrix are made to bring the calculated energies within a few cm⁻¹ of the corresponding NIST recommended data wherever available. The calculated oscillator strengths, line strengths, and radiative rates for almost all of the E1 transitions show excellent agreement with the corresponding MCDF results of Fischer. The recent results of Bhatia et al. are found to be consistently higher by 20-45%. The accuracy of the present calculation is considered to be better than the NIST accuracy ratings for various transitions.     

Energy levels and radiative rates for transitions in B-like to F-like Kr ions (Kr XXXII-XXVIII)

Energy levels, radiative rates, oscillator strengths, line strengths, and lifetimes have been calculated for transitions in B-like to F-like Kr ions, Kr XXXIII-XXVIII. For the calculations, the fully relativistic GRASP code has been adopted, and results are reported for all electric dipole (E1), electric quadrupole (E2), magnetic dipole (M1), and magnetic quadrupole (M2) transitions among the lowest 125, 236, 272, 226, and 113 levels of Kr XXXII, Kr XXXI, Kr XXX, Kr XXIX, and Kr XXVIII, respectively, belonging to the n ? 3 configurations. Comparisons are made with earlier available theoretical and experimental results, and some discrepancies have been noted and explained.     

Electric-dipole allowed and intercombination transitions among the 3d, 3d4s and 3d4p levels of Fe IV

Oscillator strengths and transition rates for the electric-dipole (E1) allowed and intercombination transitions among 3d⁵, 3d⁴4s and 3d⁴4p levels of Fe IV are calculated using the CIV3 code of Hibbert and coworkers. Using the Hartree-Fock functions up to 3d orbitals we have also optimized 4s, 4p, 4d, 4f, 5s, 5p and 5d orbitals of which 4s and 4p are taken to be spectroscopic and the remaining orbitals represent corrections to the spectroscopic orbitals or the correlation effects. The J-dependent levels of 108 LS states are included in the calculation and the relativistic effects are accounted for via the Breit-Pauli operator. Configurations are chosen in two steps: (a) two promotions were allowed from the 3p, 3d, 4s and 4p subshells, using all the orbitals; and (b) selective promotions from the 3s subshell are included, but only to the 3s and 4s orbitals. The ab initio fine-structure levels are then fine tuned to reproduce observed energy levels as closely as possible, and the resulting wavefunctions are used to calculate oscillator strengths and transition rates for all possible E1 transitions. For many of these transitions, the present results show good agreement between the length and velocity forms while for some transitions, some large disagreements are found with other available results. The complete list of weighted oscillator strengths, transition rates, and line strengths for transitions among the fine structure levels of the three lowest configurations are presented in ascending order of wavelength.