Energy Levels and Spectral Lines of Trebly Ionized Gold: Au IV

With the detection of the neutron star merger GW170817, laboratory studies of heavy elements have received great interest. This detection of gravitational waves revealed that heavy elements (such as Pt, Au, Hg, etc.) are produced in such mergers through a chain of reactions called the r-process [1]. Besides, the observations of the spectra of chemically peculiar stars from Hubble Space Telescope (HST) have resulted in the identification of lines belonging to the [4f¹⁴]5d subshell ions which includes Au [2]. This makes gold a potential tracer to study the cosmic merger events. However, it has been noticed from NIST tabulations that the available laboratory measurements for heavy elements (Z > 26) are scarce, even for their low charge states. The spectra of gold have been recorded at National Institute of Standards and Technology (USA) using 10.7-m normal incidence vacuum spectrograph (NIVS). The accuracy of the wavelength measurements for sharp and unblended lines is ±0.005 Å. In this poster, we will be presenting experimental data (Energy levels, classified lines and their uniformly scaled intensities along with theoretically calculated transition probabilities), for Au IV ion. The theoretical support for the present finding is provided within the framework of Cowan’s code calculations [3].

[1] LIGO GW170817 press release: LIGO and Virgo make first detection of gravitational waves produced by colliding neutron stars. https://www.ligo.caltech.edu/page/press-release-gw170817 [2]Wahlgren GM et al. The Abundances of Pt Au and Hg in the chemically peculiar HgMn-type stars. The Astrophysical Journal 1995, 444: 438-451 [3]Cowan RD. 1981 The theory of atomic structure and spectra (Berkeley, CA, University California) Cowan Code package for Windows by Kramida A. NIST Public DATA Repository; 2018. doi: 10.18434/T4/1502500