Collisional excitation and photoexcitation of Ca IV including a strong 3.2 m emission line

Sultana N. Nahar; Bilal Shafique

doi:10.1140/epjd/s10053-023-00622-8

2024 Impact factor 1.5

Atomic, Molecular, Optical and Plasma Physics

Eur. Phys. J. D (2023) 77: 45
https://doi.org/10.1140/epjd/s10053-023-00622-8

Regular Article – Atomic and Molecular Collisions

Collisional excitation and photoexcitation of Ca IV including a strong 3.2 $μ$ $\upmu$ m emission line

Sultana N. Nahar¹^a and Bilal Shafique²

¹ Astronomy Department, The Ohio State University, 140 W. 18th Ave, 43210, Columbus, OH, USA
² Physics Department, University of Azad Jammu and Kashmir, 13100, Muzzafarabad, Kashmir, Pakistan

^a nahar.1@osu.edu

Received: 22 October 2022
Accepted: 20 February 2023
Published online: 20 March 2023

Abstract

Graphic Abstract: We report a detailed study of features of electron impact excitation (EIE) of Ca IV (Ca IV + e $\to$ $\rightarrow$ Ca IV* + $e^{'} \to$ $e' \rightarrow$ Ca IV + h $ν + e^{'}$ $\nu + e'$ ), for the first time using the relativistic Breit–Pauli R-matrix method with a large close-coupling wave function expansion of 54 fine structure levels belonging to $n = 2, 3, 4$ $$n=2,3,4$$ complexes. Calcium lines in the infrared (IR) region are expected to be observed by the high-resolution James Webb Space Telescope. Our study predicts the presence of a strong 3.2 $μ$ $\upmu$ m emission line in IR formed due to EIE of $3 p^{5 2} P_{3 / 2}^{o} - 3 p^{5 2} P_{1 / 2}^{o}$ $3p^{5~ 2}P^o_{3/2}-3p^{5~2}P^o_{1/2}$ in Ca IV. The EIE collision strength ( $Ω$ $\Omega$ ) for the transition shows extensive resonance with enhanced background (top panel, Figure below), resulting in an effective collision strength ( $Υ$ $\Upsilon$ ) of 2.2 at about 10 $^{4}$ $$^4$$ K that increases to 9.66 around 3 $\times 10^{5}$ $\times 10^5$ k (lower panel, Figure below). The present results include $Ω$ $\Omega$ for all 1431 excitations among the 54 levels and $Υ$ $\Upsilon$ for a limited number of transitions of possible interest. We found extensive resonances in the low-energy region of $Ω$ $\Omega$ , and convergence of the resonances and of the partial waves with the 54-level wave function. At high energy, $Ω$ $\Omega$ decreases beyond the resonance region for forbidden transitions and is almost constant or decreases slowly for dipole-allowed transitions with low oscillation strength (f-values) and increases with Coulomb–Bethe behavior of ln(E) to almost a plateau for transitions with high f-values. The wave function of Ca IV was obtained from optimization of 13 configurations $3 s^{2} 3 p^{5}, 3 s 3 p^{6}, 3 s^{2} 3 p^{4} 3 d, 3 s^{2} 3 p^{4} 4 s, 3 s^{2} 3 p^{4} 4 p, 3 s^{2} 3 p^{4} 4 d, 3 s^{2} 3 p^{4} 4 f, 3 s^{2} 3 p^{4} 5 s, 3 s 3 p^{5} 3 d, 3 s 3 p^{5} 4 s, 3 s 3 p^{5} 4 p, 3 p^{6} 3 d, 3 s 3 p^{4} 3 d^{2}$ $$3s^23p^5, 3s3p^6, 3s^23p^43d, 3s^23p^44s, 3s^23p^44p, 3s^23p^44d, 3s^23p^44f, 3s^23p^45s, 3s3p^53d, 3s3p^54s, 3s3p^54p, 3p^63d, 3s3p^43d^2$$ , each with the core configuration of $1 s^{2} 2 s^{2} 2 p^{6}$ $$1s^22s^22p^6$$ , using the SUPERSTRUCTURE atomic structure program. They produce 387 fine structure levels. We report transition parameters—oscillator strength, line strength (S) and A-values-for a total of 93,296 electric dipole (E1), quadrupole (E2), octupole (E3), magnetic dipole (M1) and quadrupole (M2) transitions among these levels. The lifetimes of these levels are also presented.

Sultana Nahar and Bilal Shafique have contributed equally to this work.

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