Collaborative Research: Electron Impact Ionization and Recombination Properties of Heavy elements in Kilonovae.

Electron impact ionization (EII) and dielectronic recombination (DR) are key processes that govern the ionization balance of astrophysical plasmas. This research project will calculate accurate EII and DR cross sections for heavy elements produced in neutron star mergers (NSMs). These calculations will allow astronomers to accurately interpret the spectra of kilonovae, the transient electromagnetic emission from material ejected by NSMs, thus advancing our understanding of the production sites of the heaviest elements in the universe. The project will train a graduate student in advanced atomic physics methods, provide research opportunities to undergraduate students, and expose high school students to astronomical research. Using modern electronic structure codes, the investigators will calculate and benchmark EII and DR cross sections for ions of important elements produced by the rapid neutron capture process in NSMs. Extensive calculations will yield DR rate coefficients for temperatures consistent with the thermal (low energy) and non-thermal (high energy) electron components in kilonova ejecta. The EII cross sections will allow the investigators to explore the contributions of other ionization mechanisms that are missing from models of kilonova emission. This project advances the goals of the Windows on the Universe Big Idea. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.