Transition energies of Rn- and Fr-like actinide ions by relativistic intermediate Hamiltonian Fock-space coupled-cluster methods

► Excitations of Rn- and Fr-like ions of the four lightest actinides are studied. ► Relativity and correlation are treated at high level. ► Large, converged basis sets and model spaces are used. ► Agreement with experimentally known energies is 0.1 eV or better. ► Predictions for unknown transitions are expected to have similar accuracy.