# Photoionization of tungsten ions: experiment and theory for W$^{5+}$

## TL;DR

This study combines high-resolution experimental measurements and advanced theoretical calculations to analyze the photoionization cross sections of W$^{5+}$ ions, revealing resonance-dominated structures and achieving satisfactory agreement between methods.

## Contribution

It provides the first detailed experimental and theoretical investigation of W$^{5+}$ photoionization, employing a large basis set and high-resolution scans to understand complex tungsten ion electronic structures.

## Key findings

- Resonance-dominated photoionization cross sections observed.
- Good agreement between experimental data and Dirac-Coulomb R-matrix calculations.
- Detailed energy-dependent cross sections for multiple electronic states obtained.

## Abstract

Experimental and theoretical cross sections are reported for single-photon single ionization of W$^{5+}$ ions. Absolute measurements were conducted employing the photon-ion merged-beams technique. Detailed photon-energy scans were performed at (67$\pm$10)~meV resolution in the 20 -- 160 eV range. In contrast to photoionization of tungsten ions in lower charge states, the cross section is dominated by narrow, densely-spaced resonances. Theoretical results were obtained from a Dirac-Coulomb R-matrix approach employing a basis set of 457 levels providing cross sections for photoionization of W$^{5+}$ ions in the $4f^{14}5s^2 5p^6 5d \; {^2}{\rm D}_{3/2}$ ground level as well as the $4f^{14}5s^2 5p^6 5d \; {^2}{\rm D}_{5/2}$ and $4f^{14}5s^2 5p^6 6s \; {^2}{\rm S}_{1/2}$ 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.