Photoelectron spectroscopy of alkali halide clusters with excess electrons
We have studied excess electrons in alkali halide clusters, using a combination of a laser vaporization source, time-of-flight mass spectrometer, and magnetic bottle photoelectron electron spectrometer. We have obtained photoelectron spectra of (NaCl){sub n}{sup -}, (NaCl){sub n}Na{sup -}, (NaCl){sub n}Na{sub m}{sup -} and (KI){sub 3}K{sub m}{sup -} cluster anions contain either a single excess electron, two excess electrons, or several excess electrons. In the spectra of (NaCl){sub n}, our measured electron vertical binding energies are in excellent agreement with the calculated values. We found single excess electrons in the (NaCl){sub n}{sup -} cluster anions are mostly localized, either occupying an anion vacancy as an F-center in solids, or neutralizing a Na{sup +} ion. In a few case, electrons are delocalized on the surface of clusters. In the spectra of (NaCl){sub n}Na{sub m}{sup -}, we observed three distinct types of spectra, corresponding to three different electron accommodation modes. We suggest that in certain clusters, the excess electrons are spin paired, localizing in a single anion vacancy as an F`-center in solids or on a Na{sup +} cation to form a Na{sup -}. In other clusters, the electrons separately occupy a pair of anion vacancies as a double F-center. In the spectra of (NaCl){sub 3}Na{sub m}{sup -} and (KI){sub 3}K{sub m}{sup -}, we found features of the spectra that resemble those seen in the spectra of pure alkali metal anions after m {>=} 2. We suggest that the metallic and ionic parts in these clusters are separated, analogous to the metal and nonmetal phase separation in alkali-alkali halide metals.
- Research Organization:
- Virginia Univ., Charlottesville, VA (United States)
- OSTI ID:
- 106827
- Resource Relation:
- Other Information: TH: Thesis (Ph.D.); PBD: 1993
- Country of Publication:
- United States
- Language:
- English
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