Cowan Code Research Articles

Atomic data for dielectronic satellite lines and dielectronic recombination into Ne 5+

Energy levels, radiative transition probabilities, and autoionization rates for B-like neon (Ne 5+ ) including 1s 2 2s 2 nl , 1s 2 2s2p nl , and 1s 2 2p 2 nl ( n = 2–11 and l = 0–7) states were calculated using a multiconfigurational Hartree–Fock method (Cowan code) and a relativistic many-body perturbation theory method (RMPT) code. Autoionizing levels above three thresholds (1s 2 2s 2 1 S, 1s 2 2s2p 3 P, 1s 2 2s2p 1 P) were considered. We find that configuration mixing (2s 2 nl + 2p 2 nl ) plays an important role for all atomic characteristics. Branching ratios relative to the first threshold and the intensity factor were calculated for satellite lines and dielectronic recombination rate coefficients for the 190 odd-parity and 198 even-parity excited states. The dielectronic recombination rate coefficients including 1s 2 2s 2 nl , 1s 2 2s2p nl , and 1s 2 2p 2 nl ( n = 2–11 and l = 0–7) states were calculated. The contributions from the excited states higher than n = 11 were estimated by extrapolation of all atomic characteristics to derive the total dielectronic recombination rate coefficient. It is found that the distribution of the rate coefficients as a function of the orbital angular momentum quantum number shows a peak at l = 5. The total dielectronic recombination rate coefficient was derived as a function of electron temperature. The dielectronic satellite lines were also obtained. The state selective dielectronic recombination rate coefficients to excited states of B-like neon were obtained, which are useful for modeling Ne VI spectral lines in a recombining plasma.

Simulations of grazing-incidence pumped Ni-like Sn X-ray laser at 11.9 nm

Abstract Grazing-incidence pumped Ni-like Sn X-ray laser media at 11.9 nm (4d–4p, J = 0–1) is modelled using 1 1 2 d code EHYBRID and a post-processor code. The required atomic data are obtained using the Cowan code. In this study the pre-formed plasma is pumped on longitudinal direction with a grazing angle. Detailed simulations were performed to optimize the driving laser configurations. Relatively high gain is produced for the Ni-like Sn X-ray laser at 11.9 nm with long pre-pulse and short main pulse drive energy of only 100 mJ on 4 mm slab targets. Using low intensity pre-pulse prior to long pulse decreases the electron density gradient. X-ray resonance lines between 13 and 25 A emitted from tin plasma have been simulated using post-processor coupled with EHYBRID. The ratio of these resonance lines can be used to measure electron temperature of the laser produced Sn plasma.

Analysis of the free ion Nd3+ spectrum (Nd IV)

A recent breakthrough in the analysis of Nd IV resulted in the establishment of 37 energy levels of the ground configuration 4f3. We report here the completion to all 41 levels of this configuration. Wavelength measurements extended to 2800 Å and in higher excitation conditions lead to the classification of 1426 lines involving the excited configurations 4f25d, 4f26p, 4f26s. Owing to configuration mixing between 5p64f26p and the core-excited 5p54f4, numerous 5p64f25d–5p54f4 transitions, normally dipole-forbidden, are observed. Altogether 111 odd parity levels and 121 even parity ones have been established. Their parametric least-squares fits have rms deviations of 91 cm−1 and 37 cm−1, respectively. The interaction 5p64f25d–5p54f35d has an impact on the 4f3–4f25d transition probabilities computed by means of the Cowan codes. Theoretical values of lifetimes are reported for all the even parity levels.

The M4,5N–NNN Auger transitions in Kr

The M4,5N–NNN Auger transitions appearing as a satellite structure in the M4,5–NN Auger spectrum of krypton have been studied in detail. The M4,5N–NNN satellite Auger spectra were measured with photon energies below the 3p ionization threshold at 208 eV and above the 3p ionization threshold at 217.6 and 280 eV. The kinetic energies and intensities of the M2,3–M4,5N and M4,5N–NNN Auger transitions were calculated by using the Hartree–Fock (HF) wavefunctions with Cowan's code. The population of the 3d−14p−1 initial states produced by direct double ionization was estimated semiempirically. The most intense M4,5N–NNN Auger transitions were assigned with the aid of the calculations.

Observation and interpretation of the Tm 3+ free ion spectrum

The emission spectrum of thulium produced by a vacuum spark source was observed in the wavelength range from 700 to 2320 A on the 10.7 m normal-incidence vacuum ultraviolet spectrograph at the Paris-Meudon observatory. In the unknown spectrum of Tm IV, more than 760 lines have been identified for the first time as transitions between 157 levels of 4f115d, 33 levels of 4f116p, 9 levels of 4f116s and 10 levels of the 4f12 ground configuration. A parametric interpretation of the levels has been carried out using the Cowan codes. Configuration interaction effects are discussed, in particular with the core-excited configurations 5p54f13 and 5p54f125d. Radial Slater parameters derived from 4f12 levels are larger than those pertaining to trivalent Tm ions in compounds. A selection of 105 prominent lines is given.

Generalized oscillator strengths for some higher valence-shell excitations of argon

The valence shell excitations of argon were investigated by an angle-resolved fast-electron energy-loss spectrometer at an incident electron energy of $2500\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$, and the transition multipolarities for the excitations of $3p\ensuremath{\rightarrow}3d$, $4d$, $5s$, and $5p$ were elucidated with the help of the calculated intermediate coupling coefficients using the COWAN code. The generalized oscillator strengths for the excitations to $3{p}^{5}(3d,3{d}^{\ensuremath{'}})$, $3{p}^{5}(5p,5{p}^{\ensuremath{'}})$, and $3{p}^{5}(5s,4d)$ were measured, and the profiles of these generalized oscillator strength were analyzed. Furthermore, although the present experimental positions of the maxima for the electric-monopole and electric-quadrupole excitations in $3p\ensuremath{\rightarrow}5p$ are in agreement with the theoretical calculations [Amusia et al., Phys. Rev. A 67, 022703 (2003)], the generalized oscillator strength profiles show obvious differences. In addition, the experimental generalized oscillator strength ratios for the electric-octupole transitions in $3p\ensuremath{\rightarrow}3d$ are different from the theoretical prediction calculated by the COWAN code.

Large-scale calculation of dielectronic recombination parameters for Mg-like Fe

Energy levels, radiative transition probabilities and autoionization rates for 1s22s22p63l′nl (n = 3–12, l ⩽ n − 1) and 1s22s22p64l′nl (n = 4–7, l ⩽ n − 1) states in Mg-like iron (Fe14+) are calculated by the Hartree–Fock-relativistic method (Cowan code) and the relativistic many-body perturbation theory method (RMBPT code). Autoionizing levels above three thresholds 1s22s22p63s, 1s22s22p63p and 1s22s22p63d are considered. It is found that configuration mixings [3sns + 3pnp + 3dnd] and [3snp + 3pns + 3pnd + 3dnp] play an important role for all atomic characteristics. 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 444 odd-parity and 419 even-parity states. It is shown that the contribution of the highly-excited states is very important for calculation of total DR rates. Contributions from the excited 1s22s22p63l′nl states with n ⩾ 12 and 1s22s22p64l′nl states with n ⩾ 7 to DR rate coefficients are estimated by extrapolation of all atomic parameters. The total DR rate coefficient is derived as a function of electron temperature.

Generalized oscillator strengths for the valence-shell excitations of argon

The generalized oscillator strengths for the valence-shell excitations to $3{p}^{5}(4s,4{s}^{\ensuremath{'}})$ and $3{p}^{5}(4p,4{p}^{\ensuremath{'}})$ of argon were measured by an angle-resolved fast-electron energy-loss spectrometer at an incident electron energy of $2500\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$. The transition multipolarities for these excitations were elucidated with the help of the calculated intermediate coupling coefficients using the COWAN code. The generalized oscillator strength profiles for the electric dipole excitations to $3{p}^{5}(4s,4{s}^{\ensuremath{'}})$, the electric quadrupole and monopole excitations to $3{p}^{5}(4p,4{p}^{\ensuremath{'}})$ were analyzed and their positions of the extrema were determined. Furthermore, the generalized oscillator strength of the electric quadrupole excitation in $3p\ensuremath{\rightarrow}4p$ was determined and its profile is in general agreement with the theoretical calculations. However, the generalized oscillator strength profile of the electric monopole excitation in $3p\ensuremath{\rightarrow}4p$ is different from the theoretical calculations.

Atomic data for dielectronic recombination into C-like oxygen

Energy levels, radiative transition probabilities and autoionization rates for C-like oxygen (O2+) including 1s22s22pnl, 1s22s2p2nl and 1s22p3nl (n = 2–8, l ⩽ n − 1) states are calculated by the Hartree–Fock relativistic method (Cowan code). Autoionizing levels above the thresholds 1s22s22p 2P, 1s22s2p2 4P, 2D, 2S, 2P and 1s22p3 4S, 2D are considered. Configuration mixing 2s22pnl + 2p3nl plays an important role for all atomic characteristics. Branching ratios relative to the first threshold and intensity factors are calculated for satellite lines, and dielectronic recombination (DR) rate coefficients are presented for the excited 218 odd-parity and 218 even-parity states. The DR rate coefficients are calculated including 1s22s22pnl, 1s22s2p2nl and 1s22p3nl (n = 2–8, l ⩽ n −1) states. Contributions from the excited states with n ⩾ 8 are estimated by extrapolation of all atomic characteristics to derive the total DR rate coefficient. It is found that the orbital angular momentum quantum number l distribution of the rate coefficients shows a peak at l = 4. The total DR rate coefficient is derived as a function of electron temperature. The state-selective DR rate coefficients to excited states of C-like oxygen, which are useful for modelling O III spectral lines in a recombining plasma, are calculated as well.

Extensive analysis of 4s24p3—4s24p25s transition for RhXⅢ，PdXⅣ and AgXV

Extensive analysis of fine-structure energy levels of configurations 4s24p3(4S3/2,2P1/2,3/2, 2D1/2,3/2)and 4s24p25s(4P1/2，3/2，5/2,2P1/2,3/2, 2D3/2,5/2，2S1/2) are made for arsenic isoelectronic sequence of ions from YⅦ to AgⅩⅤ by Hartree-Fock method with relativistic corrections (HFR) using the Cowan code. The Slater parameters of fine-structure level are obtained by least-square-fit for ions mentioned above with the available experimental data, and the unknown parameters are calculated by the generalized-least-square-fit with the extra-(inter)polation method. With these new parameter values, the fine-structure energy levels of 4s24p3, 4s24p25s are computed. All of the 35 electronic-dipole transition wavelengths and its associated oscillator strengths between configurations 4s24p3 and 4s24p25s are calculated for Rh，Pd and AgⅩⅤ. The wavelength uncertainties with the available experimental values for Rh are mostly within 0.003nm. All results of Pd and AgⅩⅤ are predicted values currently anavailable in experiment.

Disentangling the emissions of highly ionized tungsten in the range 4–14 nm

In this work EBIT measurements in the spectral range of 4–7 nm with electron energies from 0.7 keV to 4 keV are compared in detail with tokamak spectra from ASDEX Upgrade. The energy and temperature dependence of spectral lines and features are investigated and an identification of the charge states W39+–W45+ for spectral lines between 4.5 nm and 6.5 nm is possible by taking cross sections from atomic data produced by plane-wave Born calculations via the Cowan code. In the range 12–14 nm the identification of spectral lines emitted by tungsten is improved even though no EBIT measurements are available, as special tokamak discharges have provided ideal possibilities for analysis. These discharges show spectra which are dominated by the emissions from a small region with a narrow electron temperature range. Therefore, only very few ion states contribute to the emission in contrast to the usual case where in the tokamak spectra the emissions of a larger number of ion states are superimposed. Tokamak spectra for varying electron temperature are also used to investigate the correlation to EBIT spectra for the quasicontinuum feature at 5 nm which is emitted by ion states W27+–W35+. We conclude that the narrower features in the EBIT spectra at a certain electron beam energy result from the smaller number of coexisting ion states.

Generalized oscillator strengths for the valence-shell excitations of neon

The generalized oscillator strengths for the valence-shell excitations to $2{p}^{5}3s$, $2{p}^{5}3p$, and $2{p}^{5}4s$ of neon were measured with an angle-resolved fast-electron energy-loss spectrometer at an incident electron energy of $2500\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$. The transition multipolarities for these excitations were elucidated with the help of the calculated intermediate-coupling coefficients using the COWAN code. The generalized oscillator strength profiles for the electric monopole, electric dipole, and electric quadrupole excitations were analyzed and their positions of the extrema were obtained. Furthermore, the experimental generalized oscillator strength ratios between the excitations to $2{p}^{5}4s{[3∕2]}_{1}$ and $2{p}^{5}4{s}^{\ensuremath{'}}{[1∕2]}_{1}$ were determined and found to be in agreement with the calculated intermediate-coupling coefficient ratio.

Excitation energies, radiative and autoionization rates, dielectronic satellite lines, and dielectronic recombination rates to excited states for B-like oxygen

Abstract Energy levels, radiative transition probabilities, and autoionization rates for B-like oxygen (O3+) including 1s22s2nl, 1s22s2pnl, and 1s22p2nl (n = 2–8, l ⩽ n − 1) states are calculated using the multiconfiguration interaction Cowan code and a relativistic many-body perturbation theory method (RMBPT) code. Autoionizing levels above three thresholds (1s22s2 1S, 1s22s2p 3P, and 1s22s2p 1P) are considered. Configuration mixing (2s2nl + 2p2nl) plays an important part in all of the atomic properties considered. Branching ratios relative to the first threshold and the intensity factor are calculated for satellite lines and dielectronic recombination rate coefficients for the excited 105 odd-parity and 94 even-parity states. The dielectronic recombination rate coefficients are calculated including 1s22s2nl, 1s22s2pnl, and 1s22p2nl (n = 2–8, l ⩽ n − 1) states. The contribution from the excited states higher than n = 8 are estimated by extrapolation of all atomic properties to derive the total dielectronic recombination rate coefficient. The orbital angular momentum quantum number distribution of the rate coefficients shows a peak at l = 5. The total dielectronic recombination rate coefficient is derived as a function of electron temperature and the dielectronic satellite lines are also obtained. The state selective dielectronic recombination rate coefficients to excited states of B-like oxygen are obtained, which are useful for modeling O IV spectral lines in a recombining plasma.

Extended Analysis of Three-times Ionized Cesium Cs IV

The spectrum of cesium was recorded in the 300–1250 Å on a 3 m normal incidence spectrograph using a triggered spark source. The 5s25p3 (6d + 7s) configurations in Cs IV spectrum were investigated. 41 out of 47 levels of two configurations have been established on the basis of 76 lines in the 344 Å–949 Å region. The observed spectrum was interpreted satisfactorily by carrying out Hartree–Fock (HF) and least-squares-fitting (LSF) calculations using Cowan Code.

Modelling of Ne-like Copper X-ray laser driven by 1.2 ps short pulse and 280 ps background pulse configuration

Detailed simulations of Ne-like Cu x-ray laser are undertaken using the EHYBRID code. The atomic physics data are obtained using the Cowan code. The optimization calculations are performed in terms of the intensity of background and the time separation between the background and the short pulse. The optimum value is obtained for the conditions of a Nd: glass laser with 1.2 ps pulse at 4.4 × 1015 W cm−2 irradiance pumping a plasma pre-formed by a 280 ps duration pulse at 5.4 × 1012 W cm−2 with peak-to-peak pulse separation set at 300 ps. X-ray resonance lines between 6 A and 15 A emitted from copper plasmas have been simulated. Free-free and free-bound emission from the Si−, Al−, Mg−, Na−, Ne− and F−like ions is calculated in the simulation.

Transitions from Autoionized Single‐ionized Tin States: A Theoretical Study of the 5s5p(3Po)nl(nl= 5d, 6s) Levels of Snii

Lines corresponding to several transitions from autoionized states of single-ionized tin were identified in a laser-produced plasma generated by 10640 A irradiation of an Sn target at a flux of 2 × 1010 W cm-2. Spectra were recorded and analyzed between 2000 and 7000 A. Theoretical analysis of Sn II was extended using relativistic Hartree-Fock calculations and configuration interactions in an intermediate-coupling scheme with the support of the Cowan code. Our calculations support the experimental value obtained by Schectman et al. in 2000 of the lifetime of 5s25d 2D3/2 and the absorption oscillator strength of the resonance transition to this level at 1400.45 A. The parametric description of 5s5p (3Po) nl (nl = 5d, 6s) of Sn II levels is improved by taking into account the far 5p3 configuration mixing effects. The results obtained in this study will allow a substantial improvement in the interpretation of the data of the ultraviolet spectrum of Sn II observed by the Goddard High Resolution Spectrograph aboard the Hubble Space Telescope.

Numerical optimization of a picosecond pulse driven Ni-like Nb x-ray laser at 20.3 nm

Detailed simulations of a Ni-like Nb x-ray laser pumped by a nanosecond prepulse followed by a picosecond main pulse are presented. The atomic physics data are obtained using the Cowan code [R. D. Cowan, The Theory of Atomic Structure and Spectra (University of California Press, Berkeley, CA, 1981)]. The optimization calculations are performed in terms of the intensity of prepulse and the time delay between the prepulse and the main pulse. A high gain over 150 cm−1 is obtained for the optimized drive pulse configuration. The ray-tracing calculations suggest that the total pump energy for a saturated x-ray laser can be reduced to less than 1 J.

Extreme UV observation of 3–3 transitions of niobium in near neon-like charge states

Abstract The emission spectra of highly ionised niobium ions generated by beam-foil excitation in the range 7–21 nm show most 3–3 transitions belonging to the neon-like ions and neighbouring Na-, Mg- and F- sequences. Wavelengths have been determined in reference to Δn=1 transitions between Rydberg states. Line identification have been made by comparison to extra- or interpolation of wavenumbers along isoelectronic sequences when data were available and to ab initio atomic structure calculations, using either a Cowan code or a fully relativistic parametric code for Ne- and F-sequences.

Dielectronic recombination-rate coefficients to excited states of Be-like oxygen and dielectronic satellite lines

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

Comprehensive theoretical and experimental analysis of Coster-Kronig electron spectra from 64-MeVS12+ions excited through He gas and C-foil targets

In Coster-Kronig electrons from the autoionizng Rydberg states of 64 MeV S 1 2 + ions excited through He gas and very thin C-foil targets, several peaks have been observed in the electron energy range up to 2.5 eV. To obtain a better understanding on low-energy electron production mechanisms in such collisions, we synthesize the expected electron spectrum by assuming that the spectral (energy) distribution of each line can be expressed with a Gaussian profile with proper resolution and compare that with the observed spectrum. Two theoretical methods, namely, the perturbation theory of the Z-expansion (MZ code) and multiconfiguration Hartree-Fock method (Cowan code) are used to calculate Auger electron energies and rates. It is found that the 1s2p15l-1s2s 1 S, 1s2p13l-1s2s 3 S, 1s 2 2p9l-1s 2 2s, 1s 2 2s2p9l-1s 2 2s 2 , 1s 2 2p 2 -7l-1s 2 2s2p 3 P, and 1s 2 2p 2 9l-1s 2 2s2p 1 P decays give a significant contribution in the electron spectrum near threshold in the range of 0-2.5 eV. Synthetic spectra have been found to reproduce the observed spectra reasonably well if the ion charge distributions are taken into account properly. Based upon the synthetic electron spectra from particular core configurations best fitted to the observed spectra, we have inferred the ion charge inside foils which can be compared with the well-established equilibrium charge after foil.