Radiative recombination rate coefficients for highly-charged tungsten ions

Partial and total radiative recombination rate coefficients are presented for highly-charged ions of tungsten with closed shells, W²⁸⁺, W³⁸⁺, W⁴⁶⁺, W⁵⁶⁺, W⁶⁴⁺, W⁷⁰⁺, and W⁷²⁺, as well as for the H-like ion W⁷³⁺ and the bare nucleus W⁷⁴⁺. The temperature range is considered. Calculations have been performed in the framework of the fully relativistic Dirac-Fock treatment of photoionization and radiative recombination processes taking into account all significant multipoles of the radiation field. We assess the influence of multipole effects on recombination rate coefficients as compared with the commonly used dipole approximation. For the first time, we show that the relativistic Maxwell-Boltzmann distribution of continuum electrons should be used at high temperature. This decreases the rate coefficient significantly compared to the nonrelativistic distribution.     

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.     

Simultaneous ionization and excitation of helium by electron impact

We present numerical results for He (1s²) (e, 2e) He⁺ reaction process for transitions to the n = 1, 2 and 3 states of He⁺ for noncoplanar symmetric geometry at incident energies of 1000 and 1600 eV. The calculations are performed using the plane wave impulse approximation (PWIA) and the 3C method (also called the Brauner, Briggs and Klar (BBK) model) that includes post collision interaction and multiple scattering effects. In both the methods we have used the highly correlated configuration interaction wave function for the ground state of helium. A comparison of the present theoretical cross sections with the recent measured data of Ren et al. [X.G. Ren, C.G. Ning, J.K. Deng, G.L. Su, S.F. Zhang, Y.R. Huang, G.Q. Li, Phys. Rev. A 72 (2005) 042718] shows reasonably good agreement.     

Excitation energies, radiative and autoionization rates, dielectronic satellite lines, and dielectronic recombination rates for excited states of Na-like W from Ne-like W

Energy levels, radiative transition probabilities, and autoionization rates for and states in Na-like tungsten (W⁶³⁺) are calculated. Cowan’s relativistic Hartree-Fock method, the relativistic multiconfiguration method implemented in the Hebrew University Lawrence Livermore Atomic Code, and the relativistic many-body perturbation theory method, are used. Autoionizing levels above the threshold 1s²2s²2p⁶ are considered. It is found that configuration mixing plays an important role for all atomic characteristics. Also strong mixing between states with 2s and 2p holes (1s²2s²2p⁵3l₁nl₂+1s²2s2p⁶3l₃nl₄) occurs. 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 excited states. It is shown that the contribution of the highly excited states is very important for calculation of total DR rates. Contributions from the autoionizing states and to the DR rate coefficients are estimated by extrapolation of all atomic parameters. The orbital angular momentum (l) distribution of the rate coefficients shows a peak at l=2. The total DR rate coefficient is derived as a function of electron temperature. The dielectronic satellite spectra of W⁶³⁺ are important for L-shell diagnostics of very high-temperature laboratory plasmas such as future ITER fusion plasmas.     

Energy levels and radiative transition rates for Ge XXXI,As XXXII,and Se XXXIII

Fine-structure energies of the 67 levels belonging to the 1s², 1s 2l$l$, 1s3l$l$, 1s4l$l$, 1s5l$l$, and 1s6l$l$ configurations of Ge XXXI, As XXXII, and Se XXXIII have been calculated using the General-Purpose Relativistic Atomic Structure Package. In addition, radiative rates, oscillator strengths, transition wavelengths, and line strengths have been calculated for all electric dipole, magnetic dipole, electric quadrupole, and magnetic quadrupole transitions among these levels. Lifetimes are also presented for all excited levels of these three ions. We have compared our results with the results available in the literature and the accuracy of the data is assessed. We predict new energy levels, oscillator strengths, and transition probabilities where no other theoretical or experimental results are available, which will form the basis for future experimental work.     

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.     

Electron-impact cross sections and rate coefficients for excitations of carbon and oxygen ions

Cross sections have been compiled for electron-impact excitation of carbon and oxygen ions (C II–VI and O II–VIII). A selection has been made to recommend “best” values for use. The resulting recommended values are fitted to an analytical formula and the fitting coefficients are given in a table. The cross sections (in the form of collision strengths) and the rate coefficients calculated therefrom are shown graphically. The reliability of the recommended data is roughly estimated.     

Determination of mass attenuation coefficients, effective atomic and electron numbers for Cr, Fe and Ni alloys at different energies

The total mass attenuation coefficients (μ_m), for Cr, Fe, Ni and Fe_xNi_1−x (x = 0.8, 0.7, 0.6, 0.5, 0.4, 0.3 and 0.2), Fe_xCr_yNi_1−(x+y) (x = 0.7, y = 0.1; x = 0.5, y = 0.2; x = 0.4, y = 0.3; x = 0.3, y = 0.3; x = 0.2, y = 0.2 and x = 0.1, y = 0.2) and Ni_xCr_1−x (x = 0.8, 0.6, 0.5, 0.4 and 0.2) alloys were measured at 22.1, 25.0, 59.5 and 88.0 keV photon energies. The samples were irradiated with 10 mCi Cd-109 and 100 mCi Am-241 radioactive point source using transmission arrangement. The γ- and X-rays were counted by a Si(Li) detector with a resolution of 160 eV at 5.9 keV. Total atomic and electronic cross-sections (σ_t and σ_e), effective atomic and electron numbers (Z_eff and N_eff) were determined experimentally and theoretically using the obtained mass attenuation coefficients for investigated 3d alloys. The theoretical mass attenuation coefficients of each alloy were estimated using mixture rule. The experimental values were compared with the calculated values for all samples.     

Proton excitation rate coefficients and cross sections among the fine-structure levels of the (2s2p)3P state in Be-like ions

Proton excitation cross sections and rate coefficients are given for the fine-structure transitions in the (2s2p)³P state in the Be-like ions C III, N IV, O V, F VI, Ne VII, Mg IX, Si XI, S XIII, Ar XV, Ca XVII, and Fe XXIII. In the low-energy region we used the semiclassical Coulomb excitation method, while for the intermediate-energy range, we used a close-coupling impact parameter method. For the temperatures tabulated here, the rate coefficients for all the transitions are better than 5%.     

Determination of mass attenuation coefficients, effective atomic and electron numbers, mean free paths and kermas for PbO, barite and some boron ores

The total mass attenuation coefficients, μ_m, for PbO, barite, colemanite, tincal and ulexite were determined at 80.1, 302.9, 356.0, 661.7 and 1250.0 keV photon energies by using NaI (Tl) scintillation detector. Effective atomic number, Z_eff, effective electron number, N_eff, total atomic cross-section, σ_t, total electronic cross-section, σ_e, mean free path, mfp, and kerma relative to air were determined experimentally and theoretically. The theoretical mass attenuation coefficients were estimated using mixture rule. The calculated values were compared with the experimental values for all samples.     

Measurement of mass attenuation coefficients,effective atomic numbers,and electron densities for different parts of medicinal aromatic plants in low-energy region

The mass attenuation coefficients(l/q) for different parts(root, flower, stem, and leaf) of three medicinal aromatic plants(Teucrium chamaedrys L. subsp. sinuatum,Rheum ribes, and Chrysophthalmum montanum) were measured using an ~(241)Am photon source in a stable geometry and calculated using the Monte Carlo N-Particle Transport Code System-extended(MCNPX) code and the WinXCOM program. The experimental and theoretical MCNPX and WinXCOM values exhibited good agreement.The measured mass attenuation coefficient values were then used to compute the effective atomic number(Z_(eff))and electron density(N_E) of the samples. The results reveal that S1-S(stem of Teucrium chamaedrys L. subsp. sinuatum) has the highest values of l/q and Zeff.     

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⁺.     

Mass attenuation coefficients,effective atomic numbers and electron densities of undoped and differently doped GaAs and InP crystals

The total mass attenuation coefficients (μ/ρ), for GaAs, GaAs (semi-insulating; S-I) GaAs:Si (N⁺), GaAs:Zn, InP:Fe, InP:Fe–As, InP:S and InP:Zn crystals were measured at 22.1, 25.0, 59.5 and 88.0 keV photon energies. The samples were irradiated with ¹⁰⁹Cd and ²⁴¹Am radioactive point sources using transmission arrangement. The X- and γ-rays were counted by a Si (Li) detector with resolution of 160 eV at 5.9 keV. Total atomic and electronic cross-sections (σ_t and σ_e), effective atomic numbers (Z_eff) and electron densities (N_el) were determined using the obtained μ/ρ values for the investigated crystals.     

Distorted-wave Born approximation for the ionization of molecules by positron and electron impact

Theoretical DWBA (distorted-wave Born approximation) cross sections for the ionization of several molecules by positron and electron impact are compared. In this work we study the effect of the projectile charge sign on the ionization cross sections when positron and electron projectiles are considered. The exchange interaction effect in case of electron projectile on the cross section is also discussed.     

Recent developments in NIKE2D for metalforming analysis and low rate impact

Analyses involving low rate impact and metalforming processes with large distortions require a robust, large deformation, finite element capability with good contact algorithms. The rapidly evolving NIKE codes are ideally suited for these types of problems. This paper highlights new metalforming simulation capabilities developed at Lawrence Livermore National Laboratory, including rezoning, adaptive time step and solution strategies, and new constutive models. Numerical examples illustrating the performance and application of NIKE2D are presented.     

Information about TS-1 and TS-2 double ionization mechanisms for positron and electron impact ionization of argon

Ejected electron angular distributions are measured for single and double ionization of argon by 500 eV positron and electron impact. Double to single ionization ratios show marked differences as a function of projectile charge. Combinations of the positron and electron data and a simple double ionization model are used to obtain differential information about the TS-1 and TS-2 mechanisms. Our analysis suggests that both mechanisms contribute roughly equally to the emission of two electrons and that interference between the two mechanisms significantly alters the ejected electron spectra.     

Energy levels,radiative rates,and lifetimes for transitions in W LVIII

Energy levels and radiative rates are reported for transitions in Cl-like W LVIII. Configuration interaction (CI) has been included among 44 configurations (generating 4978 levels) over a wide energy range up to 363 Ryd, and the general-purpose relativistic atomic structure package (grasp) adopted for the calculations. Since no other results of comparable complexity are available, calculations have also been performed with the flexible atomic code (fac), which help in assessing the accuracy of our results. Energies are listed for the lowest 400 levels (with energies up to ∼98 Ryd), which mainly belong to the 3s²3p⁵, 3s3p⁶, 3s²3p⁴3d, 3s²3p³3d², 3s3p⁴3d², 3s²3p²3d³, and 3p⁶3d configurations, and radiative rates are provided for four types of transitions, i.e. E1, E2, M1, and M2. Our energy levels are assessed to be accurate to better than 0.5%, whereas radiative rates (and lifetimes) should be accurate to better than 20% for a majority of the strong transitions.