RelativisticR-matrix close-coupling method based on the effective many-body Hamiltonian: electron-impact excitation of electric dipole-allowed and spin-forbidden transitions of the S^{4 +}ion

Abstract

Electron-impact excitation cross sections of the electric dipole-allowed 3s 2 1 S 0 → 3s3p 1 P o 1 and spin-forbidden 3s 2 1 S 0 → 3s3p 3 P o 0,1,2 transitions in Mg-like sulfur (S 4+ ) are calculated using the effective many-body Hamiltonian R-matrix close-coupling method. The calculated near-threshold electron-impact excitation cross sections for the electric dipole-allowed 3s 2 1 S 0 → 3s3p 1 P o 0 transitions are in good agreement with experimental results. The electron-impact excitation cross sections for the spin-forbidden 3s 2 1 S 0 → 3s3p 3 P o 0,1,2 transitions have been computed to benchmark theoretical accuracy against future experimental studies.

Relativistic R-matrix close-coupling method based on the effective many-body Hamiltonian: electron-impact excitation of the 3s2 1S0–3s3p1P1o electric dipole-allowed transition of the Ar6+ ion1This article is part of a Special Issue on the 10th International Colloquium on Atomic Spectra and Oscillator Strengths for Astrophysical and Laboratory Plasmas.

“…Since the theoretical basis of the effective many-body Hamiltonian R-matrix method has been described in detail [15,40,41], only the computational details are given in this section.…”

“…Accurate prediction of electron-impact excitation cross sections is a diffult task for many-electron ions [14] because of the difficulty in accurately treating electron correlation, relativity, and quantum electrodynamic (QED) effects in collisional systems [15]. Refinement and implementation of reliable theoretical methods to predict the cross sections continue to be of special importance, since the accuracy of the predicted electron-impact excitation cross sections forms the basis of plasma temperature and density diagnostics [16][17][18][19].…”

“…Badnell [30] developed the Dirac R-matrix with pseudo-states method, employing paired Laguerre spinors to represent the high-lying Rydberg states more accurately and improve the electronic structure of lowlying states of the target. An efficient alternative is to construct an effective many-body Hamiltonian that incorporates the dynamic correlation correction in the compact CI representation by means of many-body perturbation theory [15,40,41]. The use of effective many-body Hamiltonians in relativistic many-body calculations has been pioneered by Dzuba,Flambaum,and Kozlov [42] and by Safronova, Johnson, and Safronova [43].…”

“…We have recently developed and implemented a relativistic R-matrix CC method based on the effective many-body Hamiltonian in relativistic multireference many-body perturbation theory (MR-MBPT) for accurate representation of the target and collisional states of multivalence-electron ions [15,40,41]. The method accurately accounts for both static and dynamic correlations, and thus enables accurate prediction of electron impact excitations, including the effects of resonances, channel coupling, and relativity.…”

“…The method accurately accounts for both static and dynamic correlations, and thus enables accurate prediction of electron impact excitations, including the effects of resonances, channel coupling, and relativity. The method was successfully applied to the near-threshold electron impact excitation of the spin-forbidden transitions in Mg-like Ar, Mg-like S, and Zn-like Kr ions, where resonances play a major role in the excitation [15,40,41]. In the present study, the effective many-body Hamiltonian R-matrix CC method is applied to the near-threshold electron-impact excitation cross sections for the electric dipole-allowed 3s 2 1 S 0 -3s3p 1 P o 1 transitions in Mg-like argon (Ar 6+ ) and the results are compared with the benchmark laboratory measurements [3].…”