Photoionization of tungsten ions: experiment and theory for W⁵⁺

Abstract

Experimental and theoretical cross sections are reported for single-photon single ionization of W5+ ions. Absolute measurements were conducted employing the photon–ion merged-beams technique. Detailed photon-energy scans were performed at (67 ± 10) meV resolution in the 20–160 eV range. In contrast to photoionization of tungsten ions in lower charge states, the cross section is dominated by narrow, densely-spaced resonances. Theoretical results were obtained from a Dirac–Coulomb R-matrix approach employing a basis set of 457 levels providing cross sections for photoionization of W5+ ions in the 4 f 14 5 s 2 5 p 6 5 d 2 D 3 / 2 ground level as well as the 4 f 14 5 s 2 5 p 6 5 d 2 D 5 / 2 and 4 f 14 5 s 2 5 p 6 6 s 2 S 1 / 2 metastable excited levels. Considering the complexity of the electronic structure of tungsten ions in low charge states, the agreement between theory and experiment is satisfactory.

Electron-impact single ionisation of W q+ions: experiment and theory for 11 ≤ q ≤ 18

“…Motivated by the importance of tungsten in modern fusion research, a comprehensive experimental programme on studying electron-ion recombination [24][25][26], electron-impact ionisation [27,28] and photoionisation [29][30][31][32] of tungsten ions has been launched [1]. As a part of this campaign, the present study addresses electron-impact single ionisation (EISI) of W q+ ions with charge states 11 ≤ q ≤ 18, thus, extending previous experimental work on EISI of tungsten ions with charge states in the range 1-10 [33].…”

Relativistic R-matrix calculations of the photoionization of W63+ ions

“…Apart from these studies of the photoionization of neutral tungsten atoms, the photoionization of (highly charged) tungsten ions has also been extensively explored. Müller et al systematically studied, both experimentally and theoretically, the photoionization processes of lowly-charged W + -W 5+ ionsusing a photon-ion merged-beam setup at the advanced light source in Berkeley and the Dirac-Coulomb R-matrix method, respectively [29][30][31][32][33][34]. Trzhaskovskaya and Nikulin performed a systematic Dirac-Fock calculation for the photoionization of W 24+ -W 45+ and W 47+ -W 71+ ions which are of importance to the fusion plasma studies of the ASDEX-U and the ITER, respectively [35,36].…”