Accurate electron affinity of atomic cerium and excited states of its anion

Electron affinities (EA) of most lanthanide elements still remain unknown owing to their relatively lower EA values and the fairly complicated electronic structures. In the present work, we report the high-resolution photoelectron spectra of atomic cerium anion Ce^- using the slow electron velocity-map imaging method in combination with a cold ion trap. The electron affinity of Ce is determined to be 4840.62(21) cm^-1 or 0.600160(26) eV. Moreover, several excited states of Ce^- (⁴H_9/2, ⁴I_9/2, ²H_9/2, ²G_9/2, ²G_7/2, ⁴H_13/2, ²F_5/2, and ⁴I_13/2) are observed.