Valence Photoabsorption Spectroscopy of Zr and Zr+ for Astrophysical Applications

Abstract

As an element produced by the nuclear r-process, zirconium is of interest in the analysis and interpretation of astrophysical spectra. The spectra of kilonovae, resulting from binary neutron star mergers, are of particular interest. Current efforts to accurately model the spectra of kilonova AT2017gfo in non-local-thermodynamic-equilibrium (NLTE) have led to an increasing need for the atomic data of strontium, yttrium, zirconium and other r-process elements. We report valence photoabsorption spectroscopy of atomic and singly ionised zirconium using two experimental techniques, supported by relativistic atomic structure calculations, to increase current atomic data available for neutral and singly ionised zirconium. Absorption spectra of laser produced plasmas were recorded between 390 and 404 nm, and 780 and 808 nm using a dual-comb spectroscopy experiment, and between 500 nm and 1100 nm using a near infrared photoabsorption experiment, which implements a supercontinuum laser as a continuum source. A total of 384 line identifications have been made in these regions with their measured wavelength and corresponding relative absorbance listed, including 217 (193 Zr i, 24 Zr ii) newly identified features. Theoretical A-values are also provided for transitions between levels identified in the atomic structure calculations.