Searching for High-Z Elements in Neutron Star Merger Ejecta*

Multi-messenger astronomy, in which gravitational wave detections are combined with subsequent measurements across the electromagnetic spectrum, provides new opportunities to study the physics in the extreme environments of neutron star mergers. Of particular interest is a deeper understanding of the heavy-element nucleosynthesis expected to occur in the ejecta from this neutron-rich environment, the so-called r-process. The laboratory spectroscopic data on the vast range of heavy elements (Rb-U), including the lanthanides and actinides, are so severely limited at present that emission models are only in qualitative agreement with the observed spectra. To partially alleviate this situation, a computational/experimental laboratory astrophysics collaboration between Clemson University, Auburn University, the University of Georgia, and Queen's University Belfast has been formed to generate reliable line lists for a range of r-process elements from neutral to triply charged. This talk will focus on experimental progress on investigations of the electronic structure of these elements using the Compact Toroidal Hybrid plasma experiment at Auburn University and CUEBIT (Clemson University Electron Beam Ion Trap). This work is done in collaboration with the groups of Brendan McLaughlin (QUB), Michael Fogle (AU) , Phillip Stancil (UGA), and Chad Sosolik (CU).