The negative ion of lanthanum,
La–, has one of the richest bound state spectra observed for an atomic negative ion and has been proposed as a promising candidate for laser-cooling applications. In the present experiments,
La– was investigated using tunable infrared photodetachment spectroscopy. The relative signal for neutral atom production was measured with a crossed ion-beam--laser-beam apparatus over the photon energy range 585--920 meV (2120--1350 nm) to probe the continuum region above the La neutral atom ground state. Eleven prominent peaks were observed in the
La– photodetachment cross section due to resonant excitation of quasibound transient negative ion states in the continuum, which subsequently autodetach. In addition, thresholds were observed for photodetachment from several bound states of
La– to both ground and excited states of La. The present results provide information on the excited state structure and dynamics of
La– that depend crucially on multielectron correlation effects.
We present measurements of photodetachment cross sections of negative gold ions stored in a RF trap, in the energy range from about to above threshold. A number of different laser devices have been used. The results complement those described in a previous paper. The photodetachment spectrum exhibits a strong resonance, located at above ground level and a much fainter one at . These resonances can be represented as Fano profiles and reveal the presence of autodetaching excited levels of (most probably and ). Furthermore, the opening of a new photodetachment channel near 360 nm (corresponding to the first excited level of neutral Au) is accompanied by an increase of the photodetachment yield.
Abstract Negative ions, which are formed when an electron is attached to a neutral system, are unique quantum systems. The lack of a long-range Coulomb force causes the inter-electronic interactions to become relatively more important. As a consequence, the independent particle model, which adequately describes atomic structure under normal conditions, breaks down. The alkali negative ions, with a closed valence s-shell, are among the simplest anionic systems. Hence, they can favorably be used to benchmark atomic theory. In this work, we have determined the electron affinity of 85Rb by measuring the relative partial photodetachment cross section of the negative ion, leaving the residual atom in the 5p 2 P 3 / 2 excited state. Resonance ionization spectroscopy allows for state selectivity and the ability to measure the Wigner s-wave threshold onset of the photodetachment process. The electron affinity of 85Rb was determined to be 485.887(6) meV.