Visible spectra of W8+ in an electron-beam ion trap

TL;DR

This study provides new spectroscopic data for W8+ ions using visible spectra in an electron-beam ion trap, aiding fusion research by identifying key transitions and calculating atomic parameters.

Contribution

It presents the first detailed visible spectra of W8+ ions, assigns spectral lines, and compares atomic-structure calculations from two different codes for the first time.

Findings

Six visible spectral lines identified and assigned to W8+ transitions.

Good agreement between FAC and GRASP atomic-structure calculations.

Spectral simulations support the identification of six strong M1 transitions.

Abstract

To provide spectroscopic data for lowly charged tungsten ions relevant to fusion research, this work focuses on the W8+ ion. Six visible spectra lines in the range of 420-660 nm are observed with a compact electron-beam ion trap in Shanghai. These lines are assigned to W8+ based on their intensity variations as increasing electron-beam energy and the M1 line from the ground configuration in W7+. Furthermore, transition energies are calculated for the 30 lowest levels of the 4f14 5s2 5p4, 4f13 5s2 5p5 and 4f12 5s2 5p6 configurations of W8+ by using the flexible atomic code (FAC) and GRASP package, respectively. Reasonably good agreement is found between our two independent atomic-structure calculations. The resulting atomic parameters are adopted to simulate the spectra based on the collisional-radiative model implemented in the FAC code. This assists us with identification of six strong M1 transitions in 4f13 5s2 5p5 and 4f12 5s2 5p6 configurations from our experiments