New Accurate Atomic Data for Iron-group Elements for Astrophysics Applications

Modern observations of astrophysical spectra are in many cases of higher quality than those observed within a laboratory setting. This can result in the possibility of inaccurate conclusions being drawn. There is a need in astrophysics for improved atomic data for light and heavy elements across the spectrum, from IR to vacuum-UV (VUV). Accurate measurements of spectral line wavelengths and oscillator strengths are required particularly for use in stellar models and chemical abundance calculations, and in surveys such as Gaia-ESO or APOGEE and future surveys. Laboratory astrophysicists aim to measure the atomic data most useful for astronomers. Atomic data of iron-group elements are particularly important due to their high abundance and line-rich spectra. Our high-resolution Fourier Transform Spectrometry (FTS) group at Imperial College London, UK, has, supported by STFC, been providing accurate atomic data for use in astrophysics. Recent results include new Fe I oscillator strengths for use in Galactic surveys (Belmonte et al. 2017). There has been an order of magnitude improvement in atomic data for Co III (Smillie et al. 2016) and in the accuracy of energy levels and transition wavelengths for Mn II (Liggins, PhD Physics, Imperial College, 2018) and Ni II (Clear, PhD Physics, Imperial College, 2018). The first high-resolution measurements of UV transition wavelengths of Cr III are being used as wavelength standards (Smillie et al. 2008). Using new spectra recorded at the National Institute of Standards and Technology (NIST) and in the VUV at Imperial College, analysis is underway for accurate wavelengths and atomic energy levels in Mn I and Fe III. The study of the hyperfine structure of Co II is also ongoing using FTS data.