Theoretical investigation of spectroscopic properties of W²⁶⁺in EBIT plasma

Abstract

Energy levels, radiative transition wavelengths and probabilities have been studied for the ion using multiconfiguration Dirac–Fock and Dirac–Fock–Slater methods. Corona and collisional-radiative models have been applied to determine lines and corresponding configurations in a low-density electron beam ion trap (EBIT) plasma. Correlation effects for the 4f2, , ( ), ( ) configurations have been estimated by presenting configuration interaction strengths. It was determined that correlation effects are important for the transitions corresponding to weak electric octupole transitions in a single-configuration approach. Correlation effects influence the transitions by increasing transition probabilities by an order of magnitude. Identification of some lines observed in fusion plasma has been proposed. Spectra modeling shows strong increase of lines originating from the transitions. Other transitions from the 10–30 nm region can be of interest for the EBIT plasma.

Maxwellian rate coefficients for electron-impact ionization of W 26+

“…The splitting of energy levels equals 23.08 eV while the calculated single ionization threshold amounts to 830.60 eV. Our obtained energy levels, relative to the ground one, are slightly higher than GRASP2K [31] energy levels [32] except the highest one. The difference can be explained by the correlation effects which were considered in the previous calculations using configuration interaction strength [33][34][35][36].…”

Observation of electric octupole emission lines strongly enhanced by the anomalous behavior of a cascading contribution

“…Comparison with the calculated transition wavelengths shown as the blue vertical lines in the figure indicates that these lines should correspond to 4f 2 -4f 5s and 4f 5p -4f 5d transitions. The 4f 2 -4f 5s transitions are strictly forbidden in a single configuration approach, but strongly enhanced by the configuration interaction between the 4f 5s and 4f 5d levels as discussed by Jonauskas et al [27]. By increasing the electron energy further to 870 eV, three lines were additionally observed at around 8.9, 9.2, and 12.6 nm.…”