Electron-impact excitation of Ar²⁺

Abstract

Context. Emission from Ar III is seen in planetary nebulae, in H II regions, and from laboratory plasmas. The analysis of such spectra requires accurate electron impact excitation data. Aims. The aim of this work is to improve the electron impact excitation data available for Ar 2+ , for application in studies of planetary nebulae and laboratory plasma spectra. The effects of the new data on diagnostic line ratios are also studied. Methods. Electron-impact excitation collision strengths have been calculated using the R-Matrix Intermediate-Coupling FrameTransformation method and the R-Matrix Breit-Pauli method. Excitation cross sections are calculated between all levels of the configurations 3s 2 3p 4 , 3s3p 5 , 3p 6 , 3p 5 3d, and 3s 2 3p 3 nl (3d ≤ nl ≤ 5s). Maxwellian effective collision strengths are generated from the collision strength data. Results. Good agreement is found in the collision strengths calculated using the two R-Matrix methods. The collision strengths are compared with literature values for transitions within the 3s 2 3p 4 configuration. The new data has a small effect on T e values obtained from the I(λ7135 Å + λ7751 Å)/I(λ5192 Å) line ratio, and a larger effect on the N e values obtained from the I(λ7135 Å)/I(λ9 μm) line ratio. The final effective collision strength data is archived online .

Testing the Existence of Non-Maxwellian Electron Distributions in H Ii Regions After Assessing Atomic Data Accuracy

“…The target model for this system involves 10 LS terms and correlation configurations with n ≤ 4 orbitals, including an open 2p sub-shell (see Table 2). Agreement with the previous computations by Galavís et al (1995) andMunoz Burgos et al (2009) is ∼ 20% (see Table 3), but a larger discrepancy of a factor of two stands out for the 3s 2 3p 4 1 D 2 − 1 S 0 quadrupole transition due to correlation effects arising from the open 2p sub-shell in the present target model.…”

Forbidden Transitions in the Ground State Configuration of Doubly Ionized Argon

“…3 P 0 , and 3 P 2 -3 P 1 are in good agreement with [6,14,22,37]. The line strengths are also in agreement with the values of NIST.…”

“…Johnson and Kingston calculated collision strengths for electron excitation of the 3s 2 3p 4 levels of Ar III using the R-matrix method [36]. Munoz Burgos et al calculated electron-impact excitation of Ar 2+ including excitation up to the 5s subshell using R-matrix method [37].…”

Fine-structure Transitions of Ne+, Ar+, Ne2+, and Ar2+ Induced by Collisions with Atomic Hydrogen

“…This somewhat empirical estimate is consistent with the much more exhaustive study by Vieira & Krems (2017), who investigated the errors in rate coefficients resulting from small where ¡ ¢ j j is the effective collision strength (Mendoza 1983;Flower 2007;Tayal 2011) and w j is the statistical weight of the initial state. Our calculated critical densities for Ne + , Ar + and Ne 2+ , Ar 2+ , respectively, and H are shown in Figures 10 and 11 along with values of n c;e , which we calculated using Equation (10) and the effective collision strengths from Wang et al (2017) for Ne + and Ne 2+ , from Pelan & Berrington (1995) for Ar + , and from Munoz Burgos et al (2009) for Ar + 2 . For Ne + , n c (1/2; 10000; H) = 9.6 × 10 6 cm −3 and n c (1/2; 10000; e) = 6.3 × 10 5 cm −3 ; for Ar + , n c (1/2; 10000; H) = 4.7 × 10 7 cm −3 and n c (1/2; 10000; e) = 4.2 × 10 5 cm −3 ; for Ne 2+ , n c (1; 10000; H) = 2.4 × 10 6 cm −3 , n c (0; 10000; H) = 2.9 × 10 5 cm −3 and n c (1; 10000; e) = 2.1 × 10 5 cm −3 , n c (0; 10000; e) = 3.0 × 10 4 cm −3 ; for Ar 2+ , n c (1; 9000; H) = 1.5 × 10 7 cm −3 , n c (0; 9000; H) = 1.5 × 10 6 cm −3 and n c (1; 9000; e) = 2.5 × 10 5 cm −3 , n c (0; 9000; e) = 2.4 × 10 4 cm −3 .…”