Geometric and electronic structure of binary clusters containing silicon atoms

Binary clusters containing silicon atoms such as SinNam, SinCm and SinF were produced in a molecular beam using laser vaporization. The reactivity of SinNam toward NO adsorption was found to have an anti-correlation with the ionization energy of SinNam. The results of ab-initio calculation indicate that on doping with a sodium atom, the electron charge migrates from the sodium atom to the silicon cluster without disturbing seriously the original framework of the silicon cluster. Photoelectron spectroscopy of silicon-sodium cluster anions was conducted using a magnetic bottle type photoelectron spectrometer. The determined electron affinity of SinNa was also found to have clear parallelism with the ionization energy of Sin clusters. This also confirms that the parentage of the singly occupied molecular orbital (SOMO) of SinNa is the lowest unoccupied molecular orbital (LUMO) of Sin. In the case of SinF, the electron migrates from the silicon cluster to the fluorine atom, which is reflected clearly in the photoelectron spectra of SinF−1 clusters. The similarity of the photoelectron spectra of Sin − 1C− and Sin− was attributed to the similarity of their geometric structure (3 ≤ n ≤ 6). In contrast to this, Cn − 1Si− and C− exhibit different photoelectron spectra, indicating the structural difference.