Dielectronic recombination strengths and plasma rate coefficients of multiply charged ions

Abstract

Context.Dielectronic recombination (DR) has been known as the dominant electron-ion recombination process in different astrophysical and laboratory plasmas, and that it determines the level population and ionization balance over a range of temperatures. Apart from a fundamental interest into the details of this process, DR plasma rate coefficients are frequently applied to estimate plasma densities and temperatures, but have been found to be notoriously difficult to calculate as they require good knowledge of the ionic resonances, which are embedded into the continuum of the next higher charges states. Aims. In this paper we explain and demonstrate how DR resonance strengths and plasma rate coefficients can be readily computed within the framework of the Jena Atomic Calculator (Jac). In contrast to other available codes, the Jac toolbox supports a much simpler handling and control of different approximations, shell structures and temperature regions, for which doubly excited resonances need to be taken into account. Methods. A multi-configuration Dirac-Hartree-Fock expansion of all atomic states is generated and applied in order to compute the transition rates (radiative and nonradiative) that contribute to the DR process. For the plasma rate coefficients, moreover, a cascade model has been developed that automatically determines and incorporates all doubly excited configurations of interest for the given plasma temperatures. Results. To demonstrate the quite flexible use of Jac, we discuss and compare the DR of initially fluorine-like Ni 19+ ions with previous measurements and computations. Since it is based on Dirac's equation, the Jac toolbox is suitable for most ions across the periodic table.

Atomic structure and collision dynamics with highly charged ions

“…[39] The DR spectrum for the F-like Ni 19+ ions has been used as a benchmark to evaluate the JAC calculation methods. [44,45] Moreover, the 2s 2 2p 5 [ 2 P 1/2 ] → 2s2p 6 [ 2 S 1/2 ] core transition energy in the Flike Ni 19+ ions has been precisely determined and the second order QED effects are tested, which benefits from the accurate measurement of the low-lying dielectronic resonances associated with the (2s2p 6 [ 2 S 1/2 ]6s)J = 1 intermediate state and the precise calculations of the binding energy of the 6s Rydberg electrons. [46] In addition, strong mixing effects between the low lying ∆n = 0 and ∆n = 1 DR resonances have been revealed in the investigation of DR spectroscopy for the Na-like Kr 25+ ions.…”

Strong-Field Ionization Amplitudes for Atomic Many-Electron Targets

“…Similarly, the data type StrongField.AbstractSFAObservable enables one to specify the observable of choice and its resolution. All this information about the observable, target and pulse parameters finally define (an instance of) a StrongField.Computation (lower panel), and which can be utilized in JAC analogue to the previously implemented Atomic.Computation [16,29] or Cascade.Computation [30,31]. details can be obtained from JAC's User Guide [22] or by just using Julia's help facilities [32].…”

Dielectronic recombination rate coefficients of carbon-like Kr30+

“…Atomic codes such as AUTOSTRUCTURE and flexible atomic code (FAC) have achieved great success in providing the DR rate coefficients [7][8][9][10][11][12][13][14], but it is still a challenging task in the accuracy of the theoretical calculations [15,16], especially at the low collision energies due to the theoretical difficulties in dealing with the strong electronic correlation in the doubly excited resonant states [5,17]. Very recently, a newly developed code called Jena Atomic Calculator has been used to calculate the low-energy DR resonances and plasma rate coefficients of Ni 19+ ions in [18,19]. Therefore, accurate DR experiments not only supplement atomic data for plasma modeling, but also benchmark the state-of-the-art theories.…”