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 590 - 920 meV (2100 - 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. *Electronic address: walter@denison.edu. ${}^{†}$Present address: Boeing Satellite Systems,1950 E Imperial Hwy, El Segundo, CA 90245, USA. ${}^{\#}$Present address: Department of Physics and Astronomy, University of Nebraska-Lincoln, Lincoln, NE 68588, USA.

中文翻译：

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镧负离子准结合态的光解谱

镧La的负离子${}^{-}$，具有原子负离子观察到的最丰富的束缚态光谱，并已被提议作为激光冷却应用的有前途的候选者。在目前的实验中${}^{-}$使用可调红外光解光谱法进行了研究。用交叉离子束-激光束设备在光子能量范围590-920 meV（2100-1350 nm）上测量产生中性原子的相对信号，以探测La中性原子基态以上的连续区域。在La观测到11个突出峰${}^{-}$由于在连续体中准结合的瞬态负离子状态的共振激发而引起的光分离截面，随后其自动分离。此外，观察到了从La的几个键合态发生光解的阈值${}^{-}$ 对La的基态和激发态都有影响。本研究结果提供了有关La的激发态结构和动力学的信息${}^{-}$关键取决于多电子相关效应。*电子地址：walter@denison.edu。${}^{†}$现在的地址：波音卫星系统公司，1950 E Imperial Hwy，El Segundo，CA 90245，美国。 ${}^{＃}$现在的地址：美国内布拉斯加州林肯大学物理与天文学系，内华达州68588。