Atomic Data for Neutron-Capture Elements: Charge Transfer Between Cadmium and Tellurium Ions and Hydrogen

We present charge transfer (CT) rate coefficients for low-charge Cd and Te ions interacting with atomic hydrogen over the temperature range 10²-10⁶ K. Cd and Te emission lines have recently been recently discovered in planetary nebulae (Sterling et al. 2016, ApJ, 819, L9; Madonna et al. 2018, ApJ, 861, L8; Sterling 2020, Galaxies, 8, 50), and Te was possibly detected in the kilonova produced by the binary neutron star merger gravitational wave event GW170817 (Smartt et al. 2017, Nature, 551, 75). These elements can be produced by s-process nucleosynthesis in low-mass asymptotic giant branch stars, the progenitors of planetary nebulae, and by the r-process in neutron star mergers. Their abundances therefore provide important constraints to models of neutron-capture nucleosynthesis and of galactic chemical evolution. CT rate coefficients are a key ingredient for ionization equilibrium solutions of ionized nebulae, and thus for computing elemental abundances from ionic abundances. We utilized a multi-channel Landau Zener approach to compute total and final-state resolved rate coefficients for projectile ions with charges q = 2-5, and the Demkov approximation for singly-charged Cd and Te ions. Experimentally measured energies from the literature were used to improve the accuracy of our calculations. These results are needed for numerical simulations of Cd and Te in ionized nebulae that can be used to compute analytic ionization correction factors, and thus will enable more accurate determinations of the abundances of these elements in their sites of origin. We acknowledge support from NASA Georgia Space Grant Consortium awards 2018 H-61 and 2019 H-72.