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

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.

2020 ◽  
Vol 634 ◽  
pp. A7 ◽  
Author(s):  
J. Mao ◽  
N. R. Badnell ◽  
G. Del Zanna

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.


Author(s):  
Kanti M. Aggarwal ◽  
Francis P. Keenan

Recently, Fernández-Menchero et al. (2014) reported effective collision strengths ϒ for transitions among 238 fine-structure levels, belonging to the n ≤ 7 configurations of C III. They adopted the (semi-relativistic) R-matrix code (ICFT), resolved resonances in a fine energy mesh, averaged Ω over a Maxwellian distribution, and reported results over a wide range of electron temperature up to 1.8×107 K.


2011 ◽  
Vol 20 (4) ◽  
Author(s):  
Haykel Elabidi ◽  
Sylvie Sahal-Bréchot ◽  
Nébil Ben Nessib

AbstractRadiative atomic data and electron impact excitation cross sections for the 2s-2p transitions in O VI for transitions among the fine structure levels belonging to the 1s


2006 ◽  
Vol 24 (2) ◽  
pp. 235-240 ◽  
Author(s):  
V. STANCALIE ◽  
V. PAIS

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.


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