- ID:
- ivo://CDS.VizieR/J/A+A/441/831
- Title:
- Electron impact excitation of Ar XVII
- Short Name:
- J/A+A/441/831
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Energies for the lowest 49 levels among the 1s^2 and 1snl (n=2-5) configurations of Ar XVII have been calculated using the GRASP code of Dyall et al. (1989, Comput. Phys. Commun., 55, 424). Additionally, radiative rates, oscillator strengths, and line strengths are calculated for all electric dipole (E1), magnetic dipole (M1), electric quadrupole (E2), and magnetic quadrupole (M2) transitions among these levels. Furthermore, collision strengths have also been calculated for all the 1176 transitions among the above 49 levels using the Dirac Atomic R-matrix Code (DARC) of Norrington & Grant (2005, Comput. Phys. Commun., in prep.), over a wide energy range up to 580Ryd. Resonances have been resolved in the threshold region, and effective collision strengths have been obtained over a wide temperature range up to log T_e_=7.2K. Comparisons are made with the limited results available in the literature, and the accuracy of the data is assessed. Our energy levels are estimated to be accurate to better than 0.1%, whereas results for other parameters are probably accurate to better than 20%.
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- ID:
- ivo://CDS.VizieR/J/ApJS/196/24
- Title:
- Electron-impact excitation of CrII
- Short Name:
- J/ApJS/196/24
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper, we present electron-impact excitation collision strengths and Maxwellian averaged effective collision strengths for the complicated iron-peak ion CrII. We consider specifically the allowed lines for transitions from the 3d^5^ and 3d^4^4s even parity configuration states to the 3d^4^4p odd parity configuration levels. The parallel suite of R-Matrix packages, RMATRX II, which have recently been extended to allow for the inclusion of relativistic effects, were used to compute the collision cross sections. A total of 108 LS{pi}/280J{pi} levels from the basis configurations 3d^5^, 3d^4^4s, and 3d^4^4p were included in the wavefunction representation of the target including all doublet, quartet, and sextet terms. Configuration interaction and correlation effects were carefully considered by the inclusion of seven more configurations and a pseudo-corrector {overline}4d type orbital. The 10 configurations incorporated into the CrII model thus listed are 3d^5^, 3d^4^4s, 3d^4^4p, 3d^3^4s^2^, 3d^3^4p^2^, 3d^3^4s4p, 3d^4^{overline}{4d}, 3d^3^4s{overline}{4d}, 3d^3^4p{overline}{4d}, and 3d^3^{overline}{4d}^2^, constituting the largest CrII target model considered to date in a scattering calculation. The Maxwellian averaged effective collision strengths are computed for a wide range of electron temperatures 2000-100000K which are astrophysically significant. Care has been taken to ensure that the partial wave contributions to the collision strengths for these allowed lines have converged with "top-up" from the Burgess-Tully sum rule incorporated. Comparisons are made with the results of Bautista et al. and significant differences are found for some of the optically allowed lines considered.
- ID:
- ivo://CDS.VizieR/J/A+A/466/763
- Title:
- Electron-impact excitation of Fe^19+^
- Short Name:
- J/A+A/466/763
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results for the electron-impact excitation of N-like Fe as part of the RmaX network. R-matrix theory using an intermediate-coupling frame transformation method is used to obtain level-resolved collision strengths. Separate calculations are performed using different target expansions. The first is a 215 level close-coupling calculation which has the 2s^2^ 2p^3^, 2s 2p^4^, 2p^5^, 2s^2^ 2p^2^ 3l, and 2s 2p^3^ 3l configurations while the second calculation also includes the levels from the 2s^2^ 2p^2^ 4l configurations for a total of 302 close-coupling levels. The effect of the additional resonant enhancement of the larger calculation is explored and compared with a previous IRON Project report and other, more recent, calculations. As a final comparison, we model an astrophysical plasma using the results of the present calculations and previous work.
- ID:
- ivo://CDS.VizieR/J/A+A/418/371
- Title:
- Electron impact excitation of Fe XIII
- Short Name:
- J/A+A/418/371
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Energy levels and radiative rates for transitions among the lowest 97 fine-structure levels belonging to the (1s^2^2s^2^2p^6^) 3s^2^3p^2^, 3s3p^3^, 3s^2^3p3d , 3p^4^, 3s3p^2^3d and 3s^2^3d^2^ configurations of Fe XIII have been calculated using the fully relativistic GRASP code. Additionally, collision strengths for transitions among these levels have been computed using the Dirac Atomic R-matrix Code (DARC) of Norrington & Grant (2004, Comput. Phys. Commun., in prep.). Radiative rates and oscillator strengths are tabulated for all allowed transitions among the 97 fine-structure levels, while collision strengths are reported for some transitions at a few energies above thresholds. Comparisons are made with the available results, and the accuracy of the data is assessed.
- ID:
- ivo://CDS.VizieR/J/A+A/420/783
- Title:
- Electron impact excitation of Fe XVII
- Short Name:
- J/A+A/420/783
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Energies of the lowest 157 levels belonging to the (1s^2^) 2s ^2^2p^6^, 2s ^2^2p ^5^3l, 2s ^2^2p ^5^4l, 2s ^2^2p ^5^5l, 2s2p ^6^3l, 2s2p ^6^4l and 2s2p ^6^5l configurations of Fe XVII have been calculated using the GRASP code of Dyall et al. (1989, Comput. Phys. Commun., 55, 424). Additionally, radiative rates, oscillator strengths, and line strengths are calculated for all electric dipole (E1), magnetic dipole (M1), electric quadrupole (E2), and magnetic quadrupole (M2) transitions among these levels. Comparisons are made with the results already available in the literature, and the accuracy of the data is assessed. Our energy levels are expected to be accurate to better than 1%, whereas results for other parameters are probably accurate to better than 20%.
- ID:
- ivo://CDS.VizieR/J/A+A/526/A115
- Title:
- Electron-impact excitation of H-like ions
- Short Name:
- J/A+A/526/A115
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Accurate atomic data for the less abundance Fe-peak elements are required for use in X-ray astrophysical studies. We calculate high quality electron-impact excitation collision strengths and effective collision strengths for hydrogenic Cr, Mn, Fe, Co, and Ni. We use the Dirac R-matrix method, the intermediate coupling frame transformation R-matrix method, the semi-relativistic distorted-wave method and the fully-relativistic distorted-wave method to calculate collision strengths for each of the ions. The ADAS collisional-radiative codes are used to produce photon emissivity coefficients for each ion.
- ID:
- ivo://CDS.VizieR/J/A+A/420/763
- Title:
- Electron impact excitation of NiII
- Short Name:
- J/A+A/420/763
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the effects of using a 4d{bar} pseudo-orbital on the collision strengths for electron impact excitations of forbidden transitions in Ni II computed in the close coupling approximation. It is found that the resonance structures of the collision strengths are quite sensitive to the way the pseudo-orbital is created. Further, the close coupling expansion with a single 4d{bar} orbital does not converge, resulting in a poor representation of (N+1)-electrons auto-ionizing states. Much greater expansions are needed to properly represent resonance structures in electron impact excitation calculations, resulting in variations of up to factors of two, with respect to previous computations, in the Maxwellian averaged excitation rate coefficients.
- ID:
- ivo://CDS.VizieR/J/MNRAS/436/1452
- Title:
- Electron impact for OV and OVI levels
- Short Name:
- J/MNRAS/436/1452
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Radiative atomic and electron impact excitation data for OV and OVI ions have been calculated. The radiative atomic data have been calculated with the AUTOSTRUCTURE code. Besides the one-body and the two-body fine structure interactions, the two-body non-fine structure operators of the Breit-Pauli Hamiltonian, namely contact spin-spin, two-body Darwin and orbit-orbit are incorporated in AUTOSTRUCTURE. The scattering problem has been treated in the Breit-Pauli distorted wave approximation using the same code AUTOSTRUCTURE. The OV atomic calculations have been extended from 46 to 92 levels. We have calculated excitation cross sections for the OV 2s^2^-2s2p and the OVI 2s-2p transitions at energies near the corresponding excitation threshold regions. We have also calculated collision strengths for transitions from the most important levels for collisional excitation at electron energies up to 120Ry for OV and up to 140Ry for OVI. Our results have been compared with the available theoretical/experimental ones and a satisfactory agreement have been found between them.
- ID:
- ivo://CDS.VizieR/J/A+A/626/A123
- Title:
- Electron impact ionisation data
- Short Name:
- J/A+A/626/A123
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The aim of this work is to improve the modelling of ion populations in higher density, lower temperature astrophysical plasmas, of the type commonly found in lower solar and stellar atmospheres. Ion population models for these regions frequently employ the coronal approximation, which assumes conditions more suitable to the upper solar atmosphere, where high temperatures and lower densities prevail. The assumed conditions include all ions being in the ground state and steady-state equilibrium, where there is sufficient time for ionisation and recombination to take place. Using the coronal approximation for modelling the solar transition region gives theoretical lines intensities for the Li-like and Na-like isoelectronic sequences which are often factors of two to five times lower than observed. The works of Burgess & Summers (1969ApJ...157.1007B) and Nussbaumer & Storey (1975A&A....44..321N) show the important part ions in excited levels play when included in the modelling. As density increases metastable levels become populated and ionisation rates increase, whereas dielectronic recombination through highly excited levels is suppressed. Photo-ionisation is also shown by Nussbaumer & Storey to have an effect on the charge-state distribution of carbon in these regions. Their models, however, use approximations for the atomic rates to determine the ion balance. Presented here is the first stage in rates to determine the ion balance. Presented here is the first stage in updating these earlier models of carbon by using rates from up-to-date atomic calculations and more recent photo-ionising radiances. Where atomic rates were not readily available, in the case of electron impact direct ionisation and excitation-auto-ionisation, new calculations were made using the Flexible Atomic Code and Autostructure, and compared to theoretical and experimental studies. The effects each atomic process has on the ion populations as density changes is illustrated, and final results from the modelling are compared to the earlier works. Lastly, the new results for ion populations were used to predict line intensities for the solar transition region in the quiet Sun. In comparison to coronal approximation modelling the new results show significantly improved agreement with observations.
- ID:
- ivo://CDS.VizieR/J/ApJ/850/122
- Title:
- Electron-impact multiple-ionization cross sections
- Short Name:
- J/ApJ/850/122
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We compiled a set of electron-impact multiple-ionization (EIMI) cross section for astrophysically relevant ions. EIMIs can have a significant effect on the ionization balance of non-equilibrium plasmas. For example, it can be important if there is a rapid change in the electron temperature or if there is a non-thermal electron energy distribution, such as a kappa distribution. Cross section for EIMI are needed in order to account for these processes in plasma modeling and for spectroscopic interpretation. Here, we describe our comparison of proposed semiempirical formulae to available experimental EIMI cross-section data. Based on this comparison, we interpolated and extrapolated fitting parameters to systems that have not yet been measured. A tabulation of the fit parameters is provided for 3466 EIMI cross sections and the associated Maxwellian plasma rate coefficients. We also highlight some outstanding issues that remain to be resolved.
