scholarly journals R-matrix electron-impact excitation data for the C-like iso-electronic sequence

2020 ◽  
Vol 634 ◽  
pp. A7 ◽  
Author(s):  
J. Mao ◽  
N. R. Badnell ◽  
G. Del Zanna
Keyword(s):  
Electron Impact ◽  
Energy Levels ◽  
Transformation Method ◽  
Impact Excitation ◽  
Electron Impact Excitation ◽  
Atomic Data ◽  
Astrophysical Plasmas ◽  
Close Coupling ◽  
The Impact ◽  
Effective Collision

Context. Emission and absorption features from C-like ions serve as temperature and density diagnostics of astrophysical plasmas. R-matrix electron-impact excitation data sets for C-like ions in the literature merely cover a few ions, and often only for the ground configuration. Aims. Our goal is to obtain level-resolved effective collision strength over a wide temperature range for C-like ions from N II to Kr XXXI (i.e., N+ to Kr30+) with a systematic set of R-matrix calculations. We also aim to assess their accuracy. Methods. For each ion, we included a total of 590 fine-structure levels in both the configuration interaction target and close-coupling collision expansion. These levels arise from 24 configurations 2l3nl′ with n = 2−4, l = 0−1, and l′ = 0−3 plus the three configurations 2s22p5l with l = 0−2. The AUTOSTRUCTURE code was used to calculate the target structure. Additionally, the R-matrix intermediate coupling frame transformation method was used to calculate the collision strengths. Results. We compare the present results of selected ions with archival databases and results in the literature. The comparison covers energy levels, transition rates, and effective collision strengths. We illustrate the impact of using the present results on an Ar XIII density diagnostic for the solar corona. The electron-impact excitation data is archived according to the Atomic Data and Analysis Structure (ADAS) data class adf04 and will be available in OPEN-ADAS. The data will be incorporated into spectral codes, such as CHIANTI and SPEX, for plasma diagnostics.

scholarly journals R-matrix electron-impact excitation data for the N-like iso-electronic sequence

2020 ◽  
Vol 643 ◽  
pp. A95
Author(s):  
Junjie Mao ◽  
N. R. Badnell ◽  
G. Del Zanna
Keyword(s):  
Electron Impact ◽  
Plasma Diagnostics ◽  
Spectral Lines ◽  
Impact Excitation ◽  
Electron Impact Excitation ◽  
Atomic Data ◽  
Astrophysical Plasma ◽  
Wide Range ◽  
The Impact ◽  
Effective Collision

Context. Spectral lines from N-like ions can be used to measure the temperature and density of various types of astrophysical plasmas. The atomic databases of astrophysical plasma modelling codes still have room for improvement in their electron-impact excitation data sets for N-like ions, especially for R-matrix data. This is particularly relevant for future observatories (e.g. Arcus), which will host high-resolution spectrometers. Aims. We aim to obtain level-resolved effective collision strengths for all transitions up to nl = 5d over a wide range of temperatures for N-like ions from O II to Zn XXIV (i.e. O+ to Zn23+) and to assess the accuracy of the present work. We also examine the impact of our new data on plasma diagnostics by modelling solar observations with CHIANTI. Methods. We carried out systematic R-matrix calculations for N-like ions, which included 725 fine-structure target levels in both the configuration interaction target and close-coupling collision expansions. The R-matrix intermediate coupling frame transformation method was used to calculate the collision strengths, while the AUTOSTRUCTURE code was used for the atomic structures. Results. We compare the present results for selected ions with those in archival databases and the literature. The comparison covers energy levels, oscillator strengths, and effective collision strengths. We show examples of improved plasma diagnostics when compared to CHIANTI models, which use only distorted wave data as well as some using previous R-matrix data. The electron-impact excitation data are archived according to the Atomic Data and Analysis Structure (ADAS) data class adf04 and will be available in OPEN-ADAS. The data can be used to improve the atomic databases for astrophysical plasma diagnostics.

scholarly journals Effective collision strengths for electron-impact excitation of Al10+

2006 ◽  
Vol 24 (2) ◽  
pp. 235-240 ◽  
Author(s):  
V. STANCALIE ◽  
V. PAIS
Keyword(s):  
Electron Impact ◽  
Maximum Energy ◽  
Impact Excitation ◽  
Electron Collision ◽  
Electron Impact Excitation ◽  
Coupling Scheme ◽  
Close Coupling ◽  
R Matrix ◽  
Intermediate Coupling Scheme ◽  
Effective Collision

Electron collision strengths for electron-impact excitation of Li-like and Al ion are evaluated in close-coupling approximation using the multi-channel R-matrix method. Five LS target eigenstates are included in the expansion of the total wave function, consisting of the twon= 2 states withconfigurationsof 1s22s, 1s22p, and threen= 3 states withconfigurations1s23s, 1s23p, and 1s23d. Collision strengths are obtained in LS coupling using FARM code and in intermediate coupling scheme using the SUPERSTRUCTURE program. The effective collision strengths are calculated as function of temperature, up to a temperature that does not exceed half of the maximum energy in the R-matrix run.

scholarly journals Electron impact excitation rates for transitions in Mg V

2017 ◽  
Vol 95 (1) ◽  
pp. 9-20 ◽  
Author(s):  
Kanti M. Aggarwal ◽  
Francis P. Keenan
Keyword(s):  
Electron Impact ◽  
Satisfactory Agreement ◽  
Energy Levels ◽  
Impact Excitation ◽  
Electron Impact Excitation ◽  
Threshold Region ◽  
Effective Collision

Energy levels, radiative rates (A-values), and lifetimes, calculated with the GRASP code, are reported for an astrophysically important O-like ion, Mg V. Results are presented for transitions among the lowest 86 levels belonging to the 2s22p4, 2s2p5, 2p6, and 2s22p33[Formula: see text] configurations. There is satisfactory agreement with earlier data for most levels and transitions, but scope remains for improvement. Collision strengths are also calculated, with the DARC code, and the results obtained are comparable for most transitions (at energies above thresholds) with earlier work using the DW code. In the threshold region, resonances have been resolved in a fine energy mesh to determine values of effective collision strengths (Υ) as accurately as possible. Results are reported for all transitions at temperatures up to 106 K, which should be sufficient for most astrophysical applications. However, a comparison with earlier data reveals discrepancies of up to two orders of magnitude for over 60% of transitions, at all temperatures. The reasons for these discrepancies are discussed in detail.

scholarly journals Electron Impact Excitation of S III: An Assessment

Atoms ◽  
2019 ◽  
Vol 7 (3) ◽  
pp. 78
Author(s):  
Kanti M. Aggarwal
Keyword(s):  
Electron Impact ◽  
Energy Levels ◽  
Impact Excitation ◽  
Electron Impact Excitation ◽  
R Matrix ◽  
B Spline ◽  
Hartree Fock ◽  
Effective Collision

In a recent paper, Tayal et al. (Astrophys. J. Suppl. 2019, 242, 9) reported results for energy levels, radiative rates (A-values), and effective collision strengths ( Υ ) for transitions among the 198 levels of Si-like S III. For the calculations, they adopted the multi-configuration Hartree–Fock (MCHF) code for the energy levels and A-values and the B-spline R-matrix (BSR) code for Υ . Their reported results appear to be accurate for energy levels and A-values, but not for Υ . Through our independent calculations by adopting the flexible atomic code (FAC), we demonstrate that their reported results for Υ are underestimated, by up to a factor of two, and at all temperatures, particularly for the allowed transitions, but some forbidden ones as well. Additionally, for transitions involving the higher levels, the behaviour of their Υ results is not correct.

scholarly journals Electron-impact excitation of Ni II

2021 ◽  
Vol 648 ◽  
pp. A67
Author(s):  
N. L. Dunleavy ◽  
C. A. Ramsbottom ◽  
C. P. Ballance
Keyword(s):  
Fine Structure ◽  
Electron Impact ◽  
Transition Probabilities ◽  
Energy Levels ◽  
Experimental Studies ◽  
Oscillator Strengths ◽  
Impact Excitation ◽  
Electron Impact Excitation ◽  
Minimum Requirement ◽  
Effective Collision

Aims. Energy levels, transition probabilities, and oscillator strengths are calculated for the second most abundant iron peak element Ni II. The difficulty in obtaining an accurate target representation is related to the open d-shell nature of the target, which has a minimum requirement of single and double promotions from the ground state configuration to the n = 4 shells. Therefore, in order to achieve an accurate representation of the target ion, we have also included configurations containing the 4d, 5s, and 5p subshells. We have undertaken a study of the electron impact excitation of Ni II and present here the collision strengths for forbidden and allowed transitions among the lowest 800 fine-structure levels as well as the corresponding Maxwellian-averaged effective collision strengths for a range of astrophysically relevant electron temperatures. Methods. An accurate Ni II target structure was generated using the modified General-purpose Relativistic Atomic Structure Package (GRASP0) for the lowest lying 1220 jj fine-structure levels, comprising the 11 configurations: 3p63d9, 3p63d84s, 3p63d84p, 3p63d84d, 3p63d85s, 3p63d85p, 3p63d74s2, 3p63d75s2, 3p63d74s4p, 3p63d74s4d, and 3p43d94s4d. The relativistic parallel Dirac atomic R-matrix codes (DARC) were utilised in the scattering calculations to generate the collision strengths for incident electron energies between 0 and 2 Ryd and, by employing infinite dipole and non-dipole limit points, we also generated the effective collision strengths for temperatures in the range from 1000 to 400 000 K. Two separate calculations were performed, both comprised of truncated close-coupling expansions of 800 jj-levels with the first calculation retaining the theoretical ab initio energy levels generated in the GRASP0 evaluations, whereas in the second calculation these energies were shifted to their predicted National Institute of Standards and Technology (NIST) values where possible. This should provide a lower estimate on the uncertainty. Results. Comparisons are made between the radiative data and the collisional cross sections with past theoretical and experimental studies. The effective collision strengths when compared with the most recent published calculations, are found to agree to within 10% for the majority of the transitions considered. In addition, the data are used to model the spectrum of Ni II and good agreement is found with previous investigations and observations.

scholarly journals Collisional Excitation of Fluorine Like Tungsten using Relativistic Dirac Atomic R-matrix Method

2015 ◽  
Vol 2 (1) ◽  
pp. 1-14
Author(s):  
Arun Goyal ◽  
Indu Khatri ◽  
Sunny Aggarwal ◽  
A. K. Singh ◽  
Rinku Sharma ◽  
...  
Keyword(s):  
Fine Structure ◽  
Energy Levels ◽  
Impact Excitation ◽  
Electron Impact Excitation ◽  
Collisional Excitation ◽  
Distorted Wave ◽  
Fusion Plasma ◽  
R Matrix ◽  
Target States ◽  
Effective Collision

We report the new extensive calculations for collision strengths and effective collision strengths of Electron impact excitation of fine structure transitions in F-like W using fully relativistic Dirac Atomic R-matrix Code. We have included all 113 target states which belong to 2s22p5, 2s2p6, 2s22p43l, 2s2p53l, 2p63l configurations. The convergence of reported collision strengths is tested by performingthe same calculations for lesser number of target states which verify the individuality of our results.Effective collision strengthsover a wide temperature range 104-107K are computed. Further, to assess the accuracy and authenticity of our target states energies, a similar parallel calculation has also been performed using a fully relativistic distorted wave (RDW) method and a comparison of energy levels with NIST, FAC and other experimental observations has been made. We believe that the collision strength results for all forbidden transitions within the 113 fine structure levels, presented in this paper will play a substantial role in fusion plasma diagnostics.

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