Photoionization of tungsten ions: experiment and theory for W5+

A Müller,S Schippers,J Hellhund,B M McLaughlin,R A Phaneuf,A L D Kilcoyne

doi:10.1088/1361-6455/ab39c8

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 ground level as well as the and 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.

Highlights

Tungsten and its ions in low charge states are prototypical for heavy atoms with a complex electronic structure
The experimental cross section in panel a is represented by the measured energy-scan results normalized to a number of absolute measurements
The character of the W5+ photoionization cross section is strikingly different from all of the results obtained along the tungsten isonuclear sequence for Wq+ with q = 0, 1, 2, 3, and 4 which are all characterized by broad cross section features, showing a transition from moderately structured spectra to mostly smooth continua as the charge q decreases [7, 11,12,13]

Summary

Introduction

Tungsten and its ions in low charge states are prototypical for heavy atoms with a complex electronic structure. Cross section data and spectroscopic information on tungsten ions interacting with electrons and photons [4,5,6]. The present work provides experimental and theoretical cross sections for single-photon single ionization of W5+ ions. It completes a series of photoionization studies on tungsten atoms [7] and ions in low charge states [8,9,10,11,12,13]. Studies on photoionization of tungsten atoms and ions with their complex electronic structure featuring open d and f shells and comparison of experimental and theoretical results can provide benchmarks and guidance for future theoretical work on electron–ion and photon–ion interaction processes of complex many-electron systems.

Experiment

Theory

Electronic structure

Photoionization calculations

Results and discussion

Summary and conclusions