# Theoretical level energies, radiative lifetimes and transitions in W IX

## TL;DR

This paper provides detailed theoretical calculations of energy levels, transition probabilities, and lifetimes for W IX tungsten ions, filling a gap in atomic data crucial for plasma diagnostics and spectral modeling.

## Contribution

It introduces comprehensive multiconfiguration Dirac-Hartree-Fock calculations for W IX, including electron correlation effects, transition data, and lifetimes, which were previously unavailable.

## Key findings

- Calculated energy levels and transition wavelengths for W IX.
- Computed radiative lifetimes for various states.
- Provided transition probabilities for key spectral lines.

## Abstract

The atomic states of the W IX (W8+) tungsten ion lying below the W9+ ionisation threshold have been studied theoretically, employing the multiconfiguration Dirac-Hartree-Fock method with configuration interaction. The level electronic structures and their energies are presented. The electric dipole (E1), magnetic dipole (M1), electric quadrupole (E2), and magnetic quadrupole (M2) radiative transitions have been computed in order to calculate the radiative lifetimes of given states. Transition wavelengths, energies, and decay rates are also presented for selected high-intensity E1 transitions. The configuration interaction method was applied to estimate electron correlation effects. The aim of the present research was to fill a lack of atomic data for low-charged tungsten ions, which may be useful in low-temperature plasma diagnostics and may form the base for collisional-radiative modelling of spectra for low-charged tungsten ions.