Experimental and theoretical study of bound and quasibound states ofCe−

Abstract

The negative ion of cerium is investigated experimentally with tunable infrared laser photodetachment spectroscopy and theoretically with relativistic configuration interaction in the continuum formalism. The relative cross section for neutral atom production is measured with a crossed ionbeam-laser-beam apparatus over the photon energy range 0.54 -0.75 eV. A rich resonance spectrum is revealed near threshold, with at least twelve peaks observed due to transitions from bound states of Ce − to either bound or quasi-bound excited states of the negative ion. Theoretical calculations of the photodetachment cross sections enable identification of the transitions responsible for the measured peaks. Two of the peaks are due to electric-dipole-allowed bound-bound transitions in Ce − , making cerium only the second atomic negative ion that has been demonstrated to support multiple bound states of opposite parity. In addition, combining the experimental data with the theoretical analysis determines the electron affinity of cerium to be 0.628(10) eV and the fine structure splitting of the ground state of Ce − ( 4 H 7/2 -4 H 9/2 ) to be 0.09775(4) eV.

Direct experimental observation of weakly-bound character of the attached electron in europium anion

“…It is necessary to mention that some recent studies measured the EA of another lanthanide, Ce, whose yield of the anion is much higher than that of Eu −14 . Although Davis and Thompson suggested a 0.955 ± 0.026 eV EA for Ce based on their LPES experiment21, a subsequent reinterpretation of the LPES data claimed an EA of 0.660 eV22, which is consistent with later experimental results along with the theoretical predictions1923242526. Thus, no significant discrepancy exists in Ce, which is completely different from the present case, Eu.…”

La−binding energies by analysis of its photodetachment spectra

“…To be laser cooled, the atomic anion must have bound states of opposite parities that are connected by, ideally, an electric-dipole (E1) transition. Few anions possess this property and so far, only three atomic negative ions, Ce − [2], Os − [1,3,4] and La − [5,6] have been identified as possible candidates for laser cooling of negative ions. Among them, La − is deemed the most promising [6,7] due to the large strength of the proposed laser-cooling E1 transition, the short lifetime of the excited state and the large branching ratio to the initial state [8], all of which are essential to efficient laser cooling.…”

Accurate Electron Affinity of Iron and Fine Structures of Negative Iron ions

“…Like the ionization potential, the electron affinity (EA) is a fundamental parameter for understanding chemical properties of elements2122. The detailed knowledge of fine structures of anions is also required by laser cooling of negative ions232425262728.…”