GEOMETRIC AND ELECTRONIC-STRUCTURE OF BINARY CLUSTERS CONTAINING SILICON ATOMS

Binary clusters containing silicon atoms such as SinNam, SinCm and Sin F were produced in a molecular beam using laser vaporization. The reac tivity of SinNam toward NO adsorption was found to have an anti-correl ation with the ionization energy of SinNam. The results of ab-initio c alculation indicate that on doping with a sodium atom, the electron ch arge migrates from the sodium atom to the silicon cluster without dist urbing seriously the original framework of the silicon cluster. Photoe lectron spectroscopy of silicon-sodium cluster anions was conducted us ing a magnetic bottle type photoelectron spectrometer. The determined electron affinity of SinNa was also found to have clear parallelism wi th the ionization energy of Si-n clusters. This also confirms that the parentage of the singly occupied molecular orbital (SOMO) of SinNa is the lowest unoccupied molecular orbital (LUMO) of Si-n. In the case o f SinF, the electron migrates from the silicon cluster to the fluorine atom, which is reflected clearly in the photoelectron spectra of SinF - clusters. The similarity of the photoelectron spectra of Sin-1C- and Si-n(-) was attributed to the similarity of their geometric structure (3 less than or equal to n less than or equal to 6). In contrast to t his, Cn-1Si- and C-n(-) exhibit different photoelectron spectra, indic ating the structural difference.