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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.
We demonstrated the accurate prediction of a quasibound spectrum of a negative ion using a novel high-precision theoretical approach. We used La$^-$ as a test case due to a recent experiment that measured energies of 11 resonances in its photodetachm
The interaction between the field emission resonance states and the photodetached electron in an electric field is studied by semiclassical theory. An analytical expression of the photodetachment cross section is derived in the framework. It is found
We propose to use the near-threshold electron scattering data for atoms to guide the reliable experimental determination of their electron affinities (EAs), extracted using the Wigner Threshold Law, from laser photodetachment threshold spectroscopy m
Characterizing quasibound states from coupled-channel scattering calculations can be a laborious task, involving extensive manual iteration and fitting. We present an automated procedure, based on the phase shift or S-matrix eigenphase sum, that reli
Spectroscopy is a powerful tool for studying molecules and is commonly performed on large thermal molecular ensembles that are perturbed by motional shifts and interactions with the environment and one another, resulting in convoluted spectra and lim