Despite the tremendous advances in laser cooling of neutral atoms and positive ions, no negatively charged ion has been directly laser cooled. The negative ion of lanthanum, La(-), has been proposed as the best candidate for laser cooling of any atomic anion [ and , Phys. Rev. A 81, 032503 (2010)]. Tunable infrared laser photodetachment spectroscopy is used to measure the bound-state structure of La(-), revealing a spectrum of unprecedented richness with multiple bound-bound electric dipole transitions. The potential laser-cooling transition ((3)F(2)(e)→(3)D(1)(o)) is identified and its excitation energy is measured. The results confirm that La^{-} is a very promising negative ion for laser-cooling applications.

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K-shell photodetachment from C Ϫ has been investigated in the photon energy range between 280 and 285 eV using the merged ion-beam-photon-beam technique. C Ϫ ions were produced using a Cs sputtering negative-ion source, while the photons were produced by the undulator beam line 10.0.1 of the Advanced Light Source. C ϩ ions formed by double detachment were detected as a function of incident photon energy. Using this collinear arrangement, the relative cross sections were measured and compared with theoretical predictions. The measured spectrum shows the first experimental evidence of the 1s2s 2 2p 4 ( 4 P) shape resonance near 281.7 eV, which is in excellent agreement with two independent R-matrix calculations for the 1s photodetachment cross section of C Ϫ producing C ϩ .

Photodetachmentfrom negative ions in a static electric field has been studied using Cl and S These experiments were done with greater precision than previous studies and allow a quantitative comparison of data with theory. A 10-keV ion beam was sent through a region with fields of up to 1.5 kV/cm applied parallel to the beam velocity. A pulsed dye-laser beam, perpendicular to the ion beam, photoneutralized the ions. The relative cross sections were measured by detecting the resulting fast neutral atoms. Detachment below threshold and oscillations on the cross section above threshold were observed near the S threshold at 16269.5 cm ' and near the Cl threshold at 29138.3 cm '. The phase of the oscillations in the data is in good agreement with predictions for s-wave photodetachment in a static electric field, but the amplitude of the oscillations is found to be slightly reduced.PACS number(s): 32.80.Fb, 32.60.+i

Binding energies of the fine-structure levels of the indium negative ion In − are measured using infrared photodetachment threshold spectroscopy. The relative cross section for neutral atom production is measured with a crossed ion-beam-laser-beam apparatus over selected photon energy ranges between 300 and 700 meV. An s-wave threshold is observed due to the opening of the In − (5p 2 3 P 0 ) to In(5p 2 P 1/2 ) ground-state-to-ground-state transition, which determines the electron affinity of In to be 383.92(6) meV. The present result is in good agreement with previous theoretical calculations, but it differs substantially from the previously measured electron affinity and reduces the uncertainty by a factor of 150. s-wave thresholds are also observed for detachment from the excited fine-structure levels of In − , permitting accurate determination of the fine-structure intervals of 76.06(7) meV for J = 0-1 and 170.6(6) meV for J = 0-2, which are in good agreement with the previous measurements and substantially reduce the uncertainties.