Spectra of Ni V and Fe V in the Vacuum Ultraviolet

TL;DR

This paper provides improved and remeasured vacuum ultraviolet wavelengths for Ni V and Fe V ions, correcting previous calibration errors and offering new energy level data to support astrophysical observations of white dwarf stars and tests of fundamental physics.

Contribution

It presents a comprehensive remeasurement and correction of Ni V and Fe V wavelengths, along with a new energy level optimization for Ni V, enhancing data accuracy for astrophysical applications.

Findings

Corrected calibration errors in previous Ni V wavelengths

Provided new energy level data for Ni V

Improved wavelength accuracy for Fe V and Ni V in the UV range

Abstract

This work presents 97 remeasured Fe V wavelengths (1200 \r{A} to 1600 \r{A}) and 123 remeasured Ni V wavelengths (1200 \r{A} to 1400 \r{A}) with uncertainties of approximately 2m\r{A}. An additional 67 remeasured Fe V wavelengths and 72 remeasured Ni V wavelengths with uncertainties greater than 2m\r{A} are also reported. A systematic calibration error is also identified in the previous Ni V wavelengths and is corrected in this work. Furthermore, a new energy level optimization of Ni V is presented that includes level values as well as Ritz wavelengths. This work improves upon the available data used for observations of quadruply ionized nickel (Ni V) in white dwarf stars. This compilation is specifically targeted towards observations of the G191-B2B white dwarf spectrum that has been used to test for variations in the fine structure constant, $\alpha$, in the presence of strong gravitational fields. The laboratory wavelengths for these ions were thought to be the cause of inconsistent conclusions regarding the variation limit of $\alpha$ as observed through the white dwarf spectrum. These inconsistencies can now be addressed with the improved laboratory data presented here.