Relativistic many-body calculations of multipole (E1, M1, E2, M2, E3, and M3) transition wavelengths and rates between 3l4l′ excited and ground states in nickel-like ions

Wavelengths, transition rates, and line strengths are calculated for the 76 possible multipole (E1, M1, E2, M2, E3, and M3) transitions between the excited 3s²3p⁶3d⁹4l, 3s²3p⁵3d¹⁰4l, and 3s3p⁶3d¹⁰4l and the ground 3s²3p⁶3d¹⁰ states in Ni-like ions with the nuclear charges ranging from Z = 30 to 100. The relativistic many-body perturbation theory (RMBPT), including the Breit interaction, is used to evaluate energies and transition rates for multipole transitions in hole-particle systems. This method is based on relativistic many-body perturbation theory, agrees with MCDF calculations in lowest-order, includes all second-order correlation corrections, and includes corrections from negative energy states. The calculations start from a 1s²2s²2p⁶3s²3p⁶3d¹⁰ Dirac-Fock potential. First-order perturbation theory is used to obtain intermediate-coupling coefficients, and the second-order RMBPT is used to determine the matrix elements. The contributions from negative-energy states are included in the second-order E1, M1, E2, M2, E3, and M3 matrix elements. The resulting transition energies and transition rates are compared with experimental values and with results from other recent calculations. As a result, we present wavelengths and transition rates data for the selected transitions that include the 76 possible multipole (E1, M1, E2, M2, E3, and M3) transitions between the excited 3s²3p⁶3d⁹4l, 3s²3p⁵3d¹⁰4l, and 3s3p⁶3d¹⁰4l states and the ground 3s²3p⁶3d¹⁰ state in Ni-like ions. Trends of the line strengths for the 76 multipole transitions and oscillator strengths for the 13 E1 transitions as function of Z are illustrated graphically. The Z-dependence of the energy splitting for all triplet terms of the 3s²3p⁶3d⁹4l, 3s²3p⁵3d¹⁰4l, and 3s3p⁶3d¹⁰4l configurations are shown in the range of Z = 30-100.     

Energy levels, transition probabilities, and electron impact excitations for La XXX

The energy levels, spontaneous radiative decay rates, and electron impact collision strengths are calculated for La XXX. The data refer to 107 fine-structure levels belonging to the configurations (1s²2s²2p⁶)3s²3p⁶3d¹⁰, 3s²3p⁶3d⁹4l, 3s²3p⁵3d¹⁰4l, and 3s3p⁶3d¹⁰4l (l = s, p, d, f). The collision strengths are calculated with a 20-collision-energy grid in terms of the energy of the scattered electron between 10 and 10,000 eV by using the distorted-wave approximation. Effective collision strengths are obtained at seven electron temperatures: T_e (eV) = 10, 100, 300, 500, 800, 1000, and 1500 by integrating the collision strengths over a Maxwellian electron distribution. Coupled with these atomic data, a hydrodynamic code MED103 can be used to simulate the Ni-like La X-ray laser at 8.8 nm.     

Energy levels, transition probabilities, and electron impact excitation collision strengths for Xe XXVII

The energy levels, spontaneous radiative decay rates, and electron impact collision strengths are calculated for Xe XXVII. The data refer to 107 fine-structure levels belonging to the configurations (1s²2s²2p⁶)3s²3p⁶3d¹⁰, 3s²3p⁶3d⁹4l, 3s²3p⁵3d¹⁰4l and 3s3p⁶3d¹⁰4l (l = s, p, d, f). The collision strengths are calculated with a grid of 20 collision energies between 10 and 1500 eV in terms of the energy of the scattered electron, by using the distorted-wave approximation. Effective collision strengths are obtained at six temperatures, T_e (eV) = 10, 100, 300, 500, 800 and 1500, by integrating the collision strengths over a Maxwellian electron distribution. Coupled with these atomic data, a hydrodynamic code MED103 can be used to simulate the Ni-like Xe X-ray laser.     

Weighted f-values, A-values, and line strengths for the E1 transitions among 3d, 3d4s, and 3d4p levels of Fe III

Weighted oscillator strengths, weighted radiative rates, and line strengths for all the E1 transitions between 285 fine-structure levels belonging to the 3d⁶, 3d⁵4s, and 3d⁵4p configurations of Fe III are presented, in ascending order of wavelength. Calculations have been undertaken using the general configuration interaction (CI) code CIV3. The large configuration set is constructed by allowing single and double replacements from any of 3d⁶, 3d⁵4s, 3d⁵4p, and 3d⁵4d configurations to nl orbitals with n?5,l?3 as well as 6p. Additional selective promotions from 3s and 3p subshells are also included in the CI expansions to incorporate the important correlation effects in the n=3 shell. Results of some strong transitions between levels of 3d⁶, 3d⁵4s, and 3d⁵4p configurations are also presented and compared with other available calculations. It is found that large disagreements occur in many transitions among the existing calculations.     

Electron impact collision strengths and oscillator strengths for Ge-, Ga-, Zn-, Cu-, Ni-, and Co-like Au ions

Energy levels, oscillator strengths, and electron impact collision strengths have been calculated for Ge-, Ga-, Zn-, Cu-, Ni-, and Co-like Au ions. For Ni-like Au, these atomic data are obtained among the levels belonging to the configurations of ([Ne])3s²3p⁶3d¹⁰, 3s²3p⁶3d⁹nl, 3s²3p⁵3d¹⁰nl, and 3s 3p⁶3d¹⁰nl (n = 4, 5; l = 0, 1, … , n − 1). For other Au ions, more levels have been obtained with special attention to atomic data up to transitions of 5f → 3d for emission or 3d → 5f for absorption. Configuration interactions are taken into account for all levels included. Collision strengths have been obtained at 20 scattered electron energies (5-40,000 eV) and they are listed at six representative energies of 100, 500, 1000, 5000, 10,000, and 20,000 eV in this work. Effective collision strengths have been obtained by assuming a Maxwellian electron velocity distribution at 10 representative temperatures ranging from 500 to 5000 eV. The present dataset should be adequate for most applications. The energy levels are expected to be accurate to within 0.5%, while oscillator strengths and collision strengths for strong transitions are probably accurate to better than 20%. The complete dataset is available electronically from http://www.astronomy.csdb.cn/EIE/.     

Theoretical energy level spectra and transition data for 4p4d, 4p4d4f,and 4p4d configurations of W

The ab initio   quasirelativistic Hartree–Fock method developed specifically for the calculation of spectral parameters of heavy atoms and highly charged ions is used to derive transition data for a multicharged tungsten ion. The configuration interaction method is applied to include electron correlation effects. The relativistic effects are taken into account in the Breit–Pauli approximation for quasirelativistic Hartree–Fock radial orbitals. The energy level spectra, radiative lifetimes and Lande g$g$-factors are calculated for the 4p⁶4d², 4p⁶4d4f, and 4p⁵4d³ configurations of the ion W³⁶⁺. The transition wavelengths, spontaneous transition probabilities, oscillator strengths, and line strengths for the electric dipole, electric quadrupole, electric octupole, and magnetic dipole transitions among the levels of these configurations are tabulated.     

Theoretical transition probabilities, oscillator strengths, and radiative lifetimes of levels in Pb IV

Transition probabilities and oscillator strengths of 176 spectral lines with astrophysical interest arising from 5d¹⁰ns (n = 7,8), 5d¹⁰np (n = 6,7), 5d¹⁰nd (n = 6,7), 5d¹⁰5f, 5d¹⁰5g, 5d¹⁰nh (n =  6,7,8), 5d⁹6s², and 5d⁹6s6p configurations, and radiative lifetimes for 43 levels of Pb IV, have been calculated. These values were obtained in intermediate coupling (IC) and using relativistic Hartree-Fock calculations including core-polarization effects. For the IC calculations, we use the standard method of least-square fitting from experimental energy levels by means of the Cowan computer code. The inclusion in these calculations of the 5d¹⁰7p and 5d¹⁰5f configurations has facilitated a complete assignment of the energy levels in the Pb IV. Transition probabilities, oscillator strengths, and radiative lifetimes obtained are generally in good agreement with the experimental data.     

Electron impact collision strengths in Sn XXIII

The energy levels, multipole (E1, M1, E2, and M2) transition rates, and electron-impact collision strengths are calculated for Sn XXIII. The data refer to 107 fine-structure levels belonging to the configurations (1s²2s²2p⁶)3s²3p⁶3d¹⁰, 3s²3p⁶3d⁹4?, 3s²3p⁵3d¹⁰4?, and 3s3p⁶3d¹⁰4?(? = s, p, d, and f). The collision strengths are calculated with a 20-collision-energy grid in terms of the energy of the scattered electron between 37.5 and 8436 eV by using the distorted-wave approximation. Effective collision strengths are obtained at five electron temperatures, T_e (eV) = 193.89, 387.78, 581.67, 775.57, and 969.46, by integrating the collision strengths over a Maxwellian electron distribution.     

Effect of 200 MeV Ag ion irradiation on structural and electrical transport properties of Fe3O4 thin films

Thin films of Fe₃O₄ have been deposited on single crystal MgO(1 0 0) and Si(1 0 0) substrates using pulsed laser deposition. Films grown on MgO substrate are epitaxial with c-axis orientation whereas, films on Si substrate are highly 〈1 1 1〉 oriented. Film thicknesses are 150 nm. These films have been irradiated with 200 MeV Ag ions. We study the effect of the irradiation on structural and electrical transport properties of these films. The fluence value of irradiation has been varied in the range of 5 × 10¹⁰ ions/cm² to 1 × 10¹² ions/cm². We compare the irradiation induced modifications on various physical properties between the c-axis oriented epitaxial film and non epitaxial but 〈1 1 1〉 oriented film. The pristine film on Si substrate shows Verwey transition (T_V) close to 125 K, which is higher than generally observed in single crystals (121 K). After the irradiation with the 5 × 10¹⁰ ions/cm² fluence value, T_V shifts to 122 K, closer to the single crystal value. However, with the higher fluence (1 × 10¹² ions/cm²) irradiation, T_V again shifts to 125 K.     

Reactivity of hydrogen peroxide towards Fe3O4, Fe2CoO4 and Fe2NiO4

The kinetics of CRUD oxidation by H₂O₂ has been studied using aqueous suspensions of metal oxide powder. Fe₃O₄, Fe₂CoO₄ and Fe₂NiO₄ were used as model compounds for CRUD. In addition, the activation energies for the reaction between H₂O₂ and the three CRUD models were determined. The rate constants at room temperature were determined to 6.6 (±0.4) × 10⁻⁹, 3.4 (±0.4) × 10⁻⁸ and 1.6 × 10⁻¹⁰ m min⁻¹ for Fe₃O₄, Fe₂CoO₄ and Fe₂NiO₄, respectively. The corresponding activation energies are 52 ± 4, 44 ± 5 and 57 ± 7 kJ mol⁻¹, respectively. The mechanism of the reaction is briefly discussed indicating that the final solid product in all three cases is Fe₂O₃. In addition to the experimental studies, the theoretical grounds for kinetics of reactions in particle suspensions are discussed. The theoretical discussion is also used to explain the somewhat unexpected trends in reactivity observed experimentally.     

Desorption of gold nanoclusters from gold nanodispersed targets by 200 keV Au5 polyatomic ions in the elastic stopping mode: Experiment and molecular-dynamics simulation

Au nanoislet targets (∅ 2-60 nm) were bombarded by 200 keV polyatomic ions (40 keV/atom), which deposit their energy mainly in the nuclear stopping mode: ∑(dE/dx)_n = 30 keV/nm and ∑(dE/dx)_e = 2 keV/nm. The matter desorbed in the form of nanoclusters was registered by TEM. The total transfer of matter was determined by neutron-activation analysis. The total yield of the ejected gold reached high values of up to 2.6 × 10⁴ atoms per Au₅ ion. The major part (2 × 10⁴ atoms per ion Au₅) of the emission is in the form of nanoclusters. The results are compared with the data of similar experiments with 1 MeV Au₅ (200 keV/atom) and other projectiles. The analysis of the experimental data and the comparison to molecular-dynamics simulation results of the desorption process show that the desorption of Au nanoislets is induced by their melting, build-up of pressure and thermal expansion.     

Electron impact collision strengths and transition rates for extreme ultraviolet emission from Xe

The energy levels, oscillator strengths, and electron impact collision strengths are calculated for the Xe¹⁰⁺ ion using the configuration interaction scheme implemented by the Flexible Atomic Code. These data pertain to the 3917 levels belonging to the following configurations: 4s²4p⁶4d⁸, 4s²4p⁶4d⁷4f, 4s²4p⁶4d⁷5l (l = s, p, d, or f), 4s²4p⁵4d⁹, 4s²4p⁵4d⁸4f, 4s²4p⁵4d⁸5l, 4s²4p⁶4d⁶5s5p, 4s²4p⁶4d⁶5p5d. Configuration interactions among these configurations are included in the calculation. Collision strengths are obtained at 10 scattered electron energies (1-1000 eV) and are tabulated here at five representative energies of 10, 50, 100, 500, and 1000 eV. Effective collision strengths are obtained by assuming a Maxwellian electron velocity distribution at 10 temperatures ranging from 10 to 100 eV, and are tabulated at five representative temperatures of 10, 30, 50, 70 and 100 eV in this work. The whole data set should be useful for research involving extreme ultraviolet emission from Xe¹⁰⁺.     

Enthalpy measurements of La2Te3O9 and La2Te4O11

Enthalpy increment measurements on La₂Te₃O₉(s) and La₂Te₄O₁₁(s) were carried out using a Calvet micro-calorimeter. The enthalpy values were analyzed using the non-linear curve fitting method. The dependence of enthalpy increments with temperature was given as: H°(T) − H°(298.15 K) (J mol⁻¹) = 360.70T + 0.00409T² + 133.568 × 10⁵/T − 149 923 (373 ? T (K) ? 936) for La₂Te₃O₉ and H°(T) − H°(298.15 K) (J mol⁻¹) = 331.927T + 0.0549T² + 29.3623 × 10⁵/T − 114 587 (373 ? T (K) ? 936) for La₂Te₄O₁₁.     

Energies, wavelengths, and transition probabilities for Ge-like Kr, Mo, Sn, and Xe ions

Energy levels, wavelengths, transition probabilities, and oscillator strengths have been calculated for Ge-like Kr, Mo, Sn, and Xe ions among the fine-structure levels of terms belonging to the ([Ar] 3d¹⁰)4s²4p², ([Ar] 3d¹⁰)4s 4p³, ([Ar] 3d¹⁰)4s²4p 4d, and ([Ar] 3d¹⁰)4p⁴ configurations. The fully relativistic multiconfiguration Dirac-Fock method, taking both correlations within the n=4 complex and the quantum electrodynamic effects into account, have been used in the calculations. The results are compared with the available experimental and other theoretical results.     

Twisted-tape-induced swirl flow heat transfer and pressure drop in a short circular tube under velocities controlled

The twisted-tape-induced swirl flow heat transfer due to exponentially increasing heat inputs with various exponential periods (Q = Q₀ exp(t/τ), τ = 7, 14 and 23 s) and the twisted-tape-induced pressure drop were systematically measured with mass velocities, G, ranging from 4022 to 15,140 kg/m² s by an experimental water loop flow. Measurements were made on a 59.2 mm effective length which was spot-welded two potential taps on the outer surface of a 6 mm inner diameter, a 69.6 mm heated length and a 0.4 mm thickness of platinum circular test tube. The twisted tapes with twist ratios, y [=H/d = (pitch of 180° rotation)/d], of 2.39, 3.39 and 4.45 were used in this work. The relation between the swirl velocity and the pump input frequency and that between the fanning friction factor and Reynolds number (Re_d = 2.04 × 10⁴ to 9.96 × 10⁴) were clarified. The twisted-tape-induced swirl flow heat transfers with y = 2.39, 3.39 and 4.45 were compared with the values calculated by our correlation of the turbulent heat transfer for the empty tube and other worker's one for the circular tube with the twisted-tape insert. The influence of y and Reynolds numbers based on swirl velocity, Re_sw, on the twisted-tape-induced swirl flow heat transfer was investigated into details and the widely and precisely predictable correlation of the twisted-tape-induced swirl flow heat transfer was derived based on the experimental data. The correlation can describe for the twisted-tape-induced swirl flow heat transfer for the wide ranges of twist ratios (y = 2.39-4.45), mass velocities (G = 4022-15140 kg/m² s) and Reynolds numbers based on swirl velocity (Re_sw = 2.88 × 10⁴ to 1.22 × 10⁵) within −10 to +30% difference.     

Swelling and optical properties of Si3N4 films irradiated in the electronic regime

Silicon nitride layers of 140 nm thickness were deposited on silicon wafers by low pressure chemical vapour deposition (LPCVD) and irradiated at GANIL with Pb ions of 110 MeV up to a maximum fluence of 4 × 10¹³ cm⁻². As shown in a previous work these irradiation conditions, characterized by a predominant electronic slowing-down (S_e = 19.3 keV nm⁻¹), lead to damage creation and formation of etchable tracks in Si₃N₄. In the present study we investigated other radiation-induced effects like out of plane swelling and refractive index decrease. From profilometry, step heights as large as 50 nm were measured for samples irradiated at the highest fluences (>10¹³ cm⁻²). From optical spectroscopy, the minimum reflectivity of the target is shifted towards the high wavelengths at increasing fluences. These results evidence a concomitant decrease of density and refractive index in irradiated Si₃N₄. Additional measurements, performed by ellipsometry, are in full agreement with this interpretation.     

Recent advances in AMS of Cl with a 3-MV-tandem

Accelerator mass spectrometry (AMS) of ³⁶Cl (t_1/2 = 0.30 Ma) at natural isotopic concentrations requires high particle energies for the separation from the stable isobar ³⁶S and was so far the exclusive domain of tandem accelerators with at least 5 MV terminal voltage. Using terminal foil stripping and a detection setup consisting of a split-anode ionization chamber and an additional energy signal from a silicon strip detector, a ³⁶S suppression of >10⁴ at 3 MV terminal voltage was achieved. To further increase the ³⁶S suppression energy loss straggling in various counter gases (C₄H₁₀, Ar-CH₄ and C₄H₁₀-Ar) and the effect of “energy focusing” below the maximum of the Bragg curve was investigated. The comparison of experimental data with simulations and published data yielded interesting insights into the physics underlying the detectors. Energy loss, energy straggling and angular scattering determine the ³⁶S suppression. In addition, we improved ion source conditions, target backing materials and the cathode design with respect to sulfur output and cross contamination. These changes allow higher currents during measurement (³⁵Cl⁻ current ≈ 5 μA) and also increased the reproducibility. An injector to detector efficiency for ³⁶Cl ions of 8% (16% stripping yield for the 7+ charge state in the accelerator, 50% ³⁶Cl detection efficiency) was achieved, which can favorably be compared to other facilities. The memory effect in our ion source was also thoroughly investigated. Currently our measured blank value is ³⁶Cl/Cl ≈ 3 × 10⁻¹⁵ when samples with a ratio of 10⁻¹¹ are used in the same sample wheel and ³⁶Cl/Cl ≈ 5 × 10⁻¹⁶ if measured together with samples with a ratio of 10⁻¹² or below. This is in good agreement with the lowest so far published isotope ratios around 5 × 10⁻¹⁶ and demonstrates that 3 MV tandems can achieve the same sensitivity for ³⁶Cl as larger machines.     

Effects of dissolved oxygen on electrochemical and semiconductor properties of 316L stainless steel

The effects of dissolved oxygen on the electrochemical behavior and semiconductor properties of passive film formed on 316L SS in three solutions with different dissolved oxygen were studied by using polarization curve, Mott-Schottky analysis and the point defect model (PDM). The results show that higher dissolved oxygen accelerates both anodic and cathodic process. Based on Mott-Schottky analysis and PDM, the key parameters for passive film, donor density N_d, flat-band potential E_fb and diffusivity of defects D₀ were calculated. The results display that N_d(1−7 × 10²⁷ m⁻³) and D₀(1−18 × 10⁻¹⁶ cm²/s) increase and E_fb value reduces with the dissolved oxygen in solution.     

Influence of heat input waveform on transient critical heat flux of subcooled water flow boiling in a short vertical tube

The transient critical heat fluxes (CHFs) of the subcooled water flow boiling for ramp-wise heat input [Q = αt, α = 6.21 × 10⁸ to 1.63 × 10¹² W/m³ s, (q ≅ 1.08 × 10⁷ to 6.00 × 10⁷ W/m²)] and stepwise one [Q = Q_s, Q_s = 0 W/m³ at t = 0 s and Q_s = 2.95 × 10¹⁰ to 7.67 × 10¹⁰ W/m³ at t > 0 s, (q = 0 W/m² at t = 0 s and q ≅ 1.61 × 10⁷ to 3.87 × 10⁷ W/m² at t > 0 s)] with the flow velocities (u = 4.0-13.3 m/s), the inlet subcoolings (ΔT_sub,in = 86.8-153.3 K) and the inlet pressures (P_in = 742.2-1293.4 kPa) are systematically measured by an experimental water loop comprised of a pressurizer. The SUS304 tubes of inner diameters (d = 3, 6 and 9 mm), heated lengths (L = 33.15, 59.5 and 49.3 mm), L/d (=11.05, 9.92 and 5.48), and wall thickness (δ = 0.5, 0.5 and 0.3 mm) respectively with the rough finished inner surface (surface roughness, Ra = 3.18 μm) are used in this work. The experimental errors in the subcooling measure and the pressure one are ±1 K and ±1 kPa, while in the heat flux it is ±2%. The transient CHF data for the ramp-wise heat input and the stepwise one are compared with those for the exponentially increasing heat input (Q = Q₀ exp(t/τ), τ = 16.82 ms to 15.52 s) previously obtained and the dominant variables on transient CHF for heat input waveform difference are confirmed. The transient CHF data are compared with the values calculated by the steady state CHF correlations against inlet and outlet subcoolings, and the applicability of steady state CHF correlations is confirmed extending its possible validity for the reduced time, ω_p, down to 800 ms. The transient CHF data are compared with the values calculated by the transient CHF correlations against inlet and outlet subcoolings, and the influence of heat input waveform on transient CHF is clarified based on the experimental data for the ramp-wise heat input, the stepwise one and the exponentially increasing one. The dominant mechanisms of the subcooled flow boiling critical heat flux for the ramp-wise heat input, the stepwise one and the exponentially increasing one are discussed.     

Radiolysis studies of aqueous κ-carrageenan

The effects on N₂O and N₂ gas on the radiation degradation yield of aqueous kappa (κ-) carrageenan were investigated. The G_d of solution saturated with N₂O solution was expectedly much higher than in air (1.7 and 1.2 × 10⁻⁷ mol J⁻¹). On the other hand, a lower G_d of 1.1 × 10⁻⁷ mol J⁻¹ was obtained from κ-carrageenan solution saturated with N₂.The rate constant of reaction of OH radicals with sonicated and irradiated κ-carrageenan were determined using e-beam pulse radiolysis. The rate constant of OH interaction with sonicated κ-carrageenan decreased with decreasing molecular weight. On the other hand, the OH interaction with irradiated κ-carrageenan decreased but did not vary significantly with decreasing molecular weight. Metal ion (Na⁺) induced conformational transition into helical form decreased the rate constant of OH reaction with κ-carrageenan. Likewise, the G_d in aqueous form was affected by the conformational state of κ-carrageenan. The helical conformation gave a lower G_d (7 × 10⁻⁸ mol J⁻¹) than the coiled conformation (G_d = 1.2 × 10⁻⁷ mol J⁻¹).