Infrared photodetachment of Ce-: Threshold spectroscopy and resonance structure

The negative ion of cerium is investigated using tunable laser photodetachment threshold spectroscopy. The relative cross section for photodetachment from Ce− is measured over the photon energy range 0.61–0.75 eV using a crossed laser-beam–ion-beam technique. The spectrum of neutral atom production reveals a photodetachment threshold at 0.65 eV, which is interpreted as the threshold for the Ce− (4f5d26s2 4H7/2) to Ce (4f5d6s2 1G4) ground-state to ground-state transition yielding the electron affinity of Ce to be 0.65(3) eV. At least five narrow peaks are observed in the cross section over the range 0.62–0.70 eV due to negative ion resonances, and their energies and widths are measured. The results are compared to other recent experimental and theoretical studies of Ce−