The XeI Ϫ anion and the corresponding neutral X1/2, I3/2, and II1/2 electronic states have been studied by means of zero electron kinetic energy ͑ZEKE͒ and photoelectron spectroscopy. The ZEKE spectra show rich and well-resolved progressions in the low-frequency vibrations of the anion and the neutral van der Waals complexes. From our spectroscopic data we construct model potentials for the anion and three neutral states, which are compared to previously obtained potential functions for this system. The intensity of the I3/2←anion transitions relative to the X1/2 ←anion transitions in the XeI Ϫ ZEKE spectrum is considerably lower than expected from a Franck-Condon simulation based on the model potentials. Comparison with the photoelectron spectrum of XeI Ϫ indicates this is due to a small s-wave partial cross section for photodetachment to the I3/2 state.

Zero electron kinetic energy ͑ZEKE͒ spectroscopy has been utilized to study the 40 Ar 35 Cl Ϫ anion and the X1/2, I3/2 and II1/2 electronic states of neutral ArCl. Well-resolved progressions in the low-frequency vibrations of the anion and the neutral complexes are observed in the ZEKE spectra. From our spectroscopic data we construct model potential functions for the anion and three neutral states. This yields refined values for the neutral state splittings and the first accurate experimental ArCl Ϫ anion potential. Absolute uncertainties for R m and ⑀ in all potentials are estimated to be Ϯ0.08 Å and Ϯ0.6 meV, respectively.

Articles you may be interested inPhotoelectron spectroscopy and ab initio calculations of small SinSm − (n = 1,2; m = 1-4) clusters Electronic structure of vanadium cluster anions as studied by photoelectron spectroscopy Ar n Cl Ϫ clusters have been investigated by anion zero electron kinetic energy ͑ZEKE͒ and partially discriminated threshold photodetachment spectroscopy. The experiments yield size-dependent electron affinities ͑EAs͒ and electronic state splittings for the X, I, and II states accessed by photodetachment. Cluster minimum energy structures have been determined from calculations based on a ''simulated annealing'' approach employing our recently presented Ar-Cl ͑Ϫ͒ pair potentials from anion ZEKE spectroscopy ͓T. Lenzer, I. Yourshaw, M. R. Furlanetto, G. Reiser, and D. M. Neumark, J. Chem. Phys. 110, 9578 ͑1999͔͒ and various nonadditive terms. The EAs calculated without many-body effects overestimate the experimental EAs by up to 1500 cm Ϫ1 . Repulsive many-body induction in the anion clusters is found to be the dominant nonadditive effect. In addition, the attractive interaction between the chloride charge and the Ar 2 exchange quadrupole is important. These findings are consistent with our earlier results for Xe n I Ϫ , Ar n I Ϫ , and Ar n Br Ϫ clusters and highlight again the necessity of an adequate implementation of many-body effects to describe the energetics of such systems. For Ar n Cl Ϫ clusters with nϾ12 we find some deviations between experimental and calculated ͑0 K͒ EA which can be explained by the population of less stable anion structures due to the finite temperatures of the clusters in our experiments. This results in lower EAs than predicted for the corresponding global minimum energy structures.