# VIBRATIONALLY RESOLVED NEGATIVE ION PHOTOELECTRON SPECTROSCOPY OF $Nb_{8}$

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 Title: VIBRATIONALLY RESOLVED NEGATIVE ION PHOTOELECTRON SPECTROSCOPY OF $Nb_{8}$ Creators: Marcy, T. P.; Leopold, D. G. Issue Date: 1999 Abstract: We have observed a surprisingly simple, vibrationally resolved spectrum for the bare niobium octamer cluster by photoelectron spectroscopy of mass selected $Nb_{8}^{-}$ anions. The clusters were prepared in a cw cathode discharge source within a liquid nitrogen cooled flow tube (0.5 Torr), and the spectra were obtained at 488 nm (2.540 eV) with an electron kinetic energy resolution of about $5 meV (40 cm^{-1})$. The measured electron affinity of 1.513(7) eV is consistent with that obtained in the earlier anion PES $study^{a}$. In addition, the present spectrum exhibits a single clearly resolved vibrational progression in the transition between the ground electronic states of the anionic and neutral clusters. The frequency of this active mode is $185(15) cm^{-1}$ in the neutral molecule and $160(20) cm^{-1}$ in the anion, and the short progression indicates a small normal mode displacement of about $0.5 amu^{1/2}$ \AA. These results are discussed in the context of recently reported density functional $calculations^{b}$ on Nb8 and $Nb8^{-}$ URI: http://hdl.handle.net/1811/19431 Other Identifiers: 1999-TB-02