Geometric and electronic structure of binary clusters containing silicon atoms

Abstract

Binary clusters containing silicon atoms such as Si n Na m , Si n C m and Si n F were produced in a molecular beam using laser vaporization. The reactivity of Si n Na m toward NO adsorption was found to have an anti-correlation with the ionization energy of Si n Na m . 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 Si n Na was also found to have clear parallelism with the ionization energy of Si n clusters. This also confirms that the parentage of the singly occupied molecular orbital (SOMO) of Si n Na is the lowest unoccupied molecular orbital (LUMO) of Si n . In the case of Si n F, the electron migrates from the silicon cluster to the fluorine atom, which is reflected clearly in the photoelectron spectra of Si n F −1 clusters. The similarity of the photoelectron spectra of Si n − 1 C − and Si n − was attributed to the similarity of their geometric structure ( 3 ≤ n ≤ 6). In contrast to this, C n − 1 Si − and C − exhibit different photoelectron spectra, indicating the structural difference.