Measurement of the electron affinity of atomic Ce

Photoelectron spectra of Ce^- obtained using both 2.33- and 3.49-eV photon energies resolve numerous transitions between the ⁴H7/2 (⋯4f 5d² 6s²) anion ground state and excited neutral states, in addition to transitions from excited anion states to the ground and excited neutral states. Building on the theoretical work of O'Malley and Beck [S. M. O'Malley and D. R. Beck, Phys. Rev. A 74, 042509 (2006)] and the known term energies of Ce excited states, we determined the adiabatic electron affinity of Ce to be 0.570(20) eV, which is lower than previously reported experimental values. The term energy of the lowest-energy excited anion state arising from the ⋯4f 5d 6s² 6p configuration was also determined to be 0.210(20) eV.