Photoionization of the valence shells of the neutral tungsten atom

Abstract

Results from large-scale theoretical cross section calculations for the total photoionization of the 4f, 5s, 5p and 6s orbitals of the neutral tungsten atom using the Dirac Coulomb R-matrix approximation (DARC: Dirac-Atomic R-matrix codes) are presented. Comparisons are made with previous theoretical methods and prior experimental measurements. In previous experiments a time-resolved dual laser approach was employed for the photo-absorption of metal vapours and photo-absorption measurements on tungsten in a solid, using synchrotron radiation. The lowest ground state level of neutral tungsten is $5{\mathrm{p}}^{6}5{\mathrm{d}}^{4}6{\mathrm{s}}^2{}^5{\mathrm{D}}_J$, with $J$=0, and requires only a single dipole matrix for photoionization. To make a meaningful comparison with existing experimental measurements, we statistically average the large-scale theoretical PI cross sections from the levels associated with the ground state $5{\mathrm{p}}^{6}5{\mathrm{d}}^{4}6{\mathrm{s}}^2{}^5{\mathrm{D}}_J[J=0,1,2,3,4]$ levels and the $5{\mathrm{d}}^{5}6s{}^7{\mathrm{S}}_3$ excited metastable level. As the experiments have a self-evident metastable component in their ground state measurement, averaging over the initial levels allows for a more consistent and realistic comparison to be made. In the wider context, the absence of many detailed electron-impact excitation (EIE) experiments for tungsten and its multi-charged ion stages allows current photoionization measurements and theory to provide a road-map for future electron-impact excitation, ionization and di-electronic cross section calculations by identifying the dominant resonance structure and features across an energy range of hundreds of eV.

10 pages, 3 figures, accepted for publication in J Phys B: At. Mol. Opt. Phys

References in corpus (3)

• Photoionization Cross-Sections for the trans-iron element Se${}^{+}$ from 18 eV to 31 eV
• Photoionization of the $3s^{2}3p^4{}^{3}P$ and the $3s^{2}3p^4{}^{1}D,{}^{1}S$ states of sulfur: experiment and theory
• Valence-shell photoionization of Ag-like Xe${}^{7+}$ ions : experiment and theory

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