Relativistic Coupled Cluster Calculations with Variational Quantum Electrodynamics Resolve the Discrepancy between Experiment and Theory Concerning the Electron Affinity and Ionization Potential of Gold

The first ionization potential (IP) and electron affinity (EA) of the gold atom have been determined to an unprecedented accuracy using relativistic coupled cluster calculations up to the pentuple excitation level including the Breit and QED contributions. We reach meV accuracy (with respect to the experimental values) by carefully accounting for all individual contributions beyond the standard relativistic coupled cluster approach. Thus, we are able to resolve the long-standing discrepancy between experimental and theoretical IP and EA of gold.