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(a) Polarization for the photon emission from anisotropic excited states through different transitions (as given in Table 6) for K-like, Ar-like, Cl-like, S-like and P-like tungsten ions as a function of incident electron energy; (b) Polarization for the photon emission from anisotropic excited states through different transitions (as given in Table 6) for Si-like, Al-like, Mg-like and Na-like tungsten ions as a function of incident electron energy.
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Electron impact excitation of highly charged tungsten ions in the framework of a fully relativistic distorted wave approach is considered in this paper. Calculations of electron impact excitation cross-sections for the M- and L-shell transitions in the tungsten ions Wn+ (n = 44–66) and polarization of the decay of photons from the excited tungsten...
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Citations
... For example, the measurements reported by Beiersdorfer and his co-workers [14][15][16][17] from electron beam ion trap at the Lawrence Livermore National have identified the tungsten ions W n + (where n varies from 44 to 66) present in the EBIT plasma and recorded their spectra having possible intense lines coming from the electron impact l -and M-shell excitations. In the light of this experiment, only for the identified tungsten ions and their various M-and l -shell transitions, we had recently performed extensive calculations of the electron impact excitation cross-section using fully relativistic distorted wave (RDW) theory [18][19][20][21] . The cross-sections results were reported in the wide range of incident electron energies as in the ITER plasma all electron impact energies are possible. ...
... In continuation to our earlier work [18][19][20][21] as mentioned above, in the present work, we study the electron impact excitation of N-shells of the four tungsten ions viz. Se-through Ga-like tungsten ions having 4 s 2 4 p n ( n = 1, 2, 3, 4) ground state configurations. ...
Study of electron impact excitation of W⁴⁰⁺ (Se-like), W⁴¹⁺ (As-like), W⁴²⁺ (Ge-like), and W⁴³⁺ (Ga-like) ions using fully relativistic distorted wave theory has been presented. The excitation cross-sections of E1 and E2 allowed transitions of these ions are reported across the wide range of incident electron energies from excitation threshold to 20 keV. The obtained cross-sections of all the transitions of the four ions are fitted with an analytical expression for the applications in the plasma modelling. Further, using the magnetic sublevel cross-sections, the degree of linear polarization of the photon emissions from the electron impact excited anisotropic states of tungsten ions through the dipole allowed transitions are also calculated.
We have presented atomic data including energies, transition wavelengths, radiative rates and oscillator strengths, which are evaluated for W LXIV, for the lowest 100 fine structure levels and multipole transitions (E1, E2, M1 and also for M2). For W LXIV, we identified the 21 in electric dipole, 33 in electric quadrupole, 28 in magnetic dipole and 21 in magnetic quadrupole soft x-ray (SXR) transitions, as well as 1 in electric dipole extreme ultraviolet (EUV) transitions from the ground state. Furthermore, we have analysed the photoionization cross section and ionization potential of 3s, 3p and 3d levels of Na-like W at five different photoelectron energies by employing the FAC code. Line intensity ratios and electron density for W LXIV have also been reported, which will be useful and necessary for plasma diagnostics, including modelling for future International Thermonuclear Experimental Reactor (ITER) investigations. We assume that our observations will be useful for cell biology, biophysics, fusion plasma research, as well as astrophysical studies and their applications.
Extended computation of energy levels and radiative data such as transition wavelengths, transition probabilities, and oscillator strengths for electric dipole (E1) transitions are performed for chlorine-like Tungsten ions WLVIII using the fully relativistic Flexible Atomic Code (FAC). Comparisons are done with the accessible experimental results and theoretical data in the literature. Close agreement has been found ensuring the accuracy and reliability of our results. We have studied collisional excitation cross section and presented magnetic sublevel cross sections for excitations from the ground state 3s\({}^{2}\) 3p\({}^{52}\)P\({}^{o}\)\({}_{3/2}\) to the first excited state 3s\({}^{2}\)3p\({}^{4}\)3d \({}^{4}\)D\({}_{3/2}\) of W\({}^{57+}\) as a function of incident electron energy. We calculate new data for several levels where no other theoretical and/or experimental results are available. Our work will help to develop diagnostics for evaluating tungsten concentrations in fusion plasmas and provide platform for modeling predictions.
We present comprehensive and elaborate study of W LVI (K-likeW55+) by using multi-configuration Dirac-Fock method (MCDF). We have included relativistic corrections, QED (Quantum electrodynamics) and Breit corrections in our computation. We have reported energy levels and radiative data for multipole transitions i.e. electric dipole (E1), electric quadrupole (E2), magnetic dipole (M1) and magnetic quadrupole (M2) within lowest 142 fine structure levels and predicted soft x-ray transition (SXR) and extreme ultraviolet transitions (EUV) from higher excited states to ground state. We have compared our calculated data with energy levels compiled by NIST and other available results in literature and small discrepancies found with them are discussed. Since only few lowest levels are only available in the literature, therefore for checking excitation energies of higher excited states, we have performed same calculations with distorted wave method. Furthermore, we have also provided relative population for first five excited states, partition function and thermodynamic quantities for both W LVI and studied their variations with temperature. We believe that our reported new atomic data of W LVI may be useful in identification and analysis of spectral lines from various astrophysical and fusion plasma sources and also beneficial in plasma modeling.
Electron-impact excitation of tungsten ions Wq+(q = 40 − 43) has been studied using the fully relativistic distorted wave (RDW) theory. The excitation cross-sections of selected electric dipole allowed transitions of these ions to be determined for the incident electron energies from the excitation threshold to 20 keV. Further, the calculated cross-section results are fitted with an analytical expression for direct applications in plasma modeling. In addition, using the density matrix theory, the linear polarization of the photons emitted from the excited tungsten ions when decay to their respective ground states is presented.
Fully relativistic distorted wave theory has been utilized to study the electron-impact excitation of highly charged tungsten ions viz. Y-like (W³⁵⁺), Sr-like (W³⁶⁺), Rb-like (W³⁷⁺) and Br-like (W³⁹⁺). Electric dipole transitions pertaining to n = 4 → n′ = 4 states have been considered in these four ions. The electron excitation cross-sections are calculated for these ions in the wide range of electron-impact energies from excitation threshold to 20 keV. The required relativistic bound states wave functions for the initial and excited states of the ions are obtained using GRASP2k code. The accuracy of the computed wave functions is ascertained by comparing the calculated energies and oscillator strengths for the considered transitions with the available theoretical and experimental results. For the direct application of the cross-sections to the plasma modelling our calculated cross-sections are fitted to suitable analytical expressions. Further, the degree of linear polarization of the emitted photons due to the decay of the electron from the excited tungsten ions to their respective ground states is also calculated using density matrix theory. There are no previous calculations available for the cross-sections and polarizations to compare with our results of these ions.
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A systematic study of the electron impact excitation of highly charged Rb-like W37+ through
Br-like W39+ tungsten ions has been done using fully relativistic distorted wave theory. The cross sections
are calculated for various transitions in the electron impact energy range from the excitation threshold to
20 keV. Analytic fitting of the calculated cross sections are also provided so that these can be directly used
in any plasma model. Linear polarization of the emitted photons, due to decay of the different electron
excited states of the tungsten ions has also been obtained and reported.
