Photoelectron spectroscopy of silicon-carbon cluster anions (Si _nC_m ^-)

Photoelectron spectra of Si_n,C_m ^- cluster anions (1≤n≤7 and 1≤m≤5) were measured at the photon energies of 3.49 eV, by using a magnetic bottle electron spectrometer. The Si _nC_m ^- clusters were produced either by a laser vaporization of a silicon-carbon mixed rod or by two laser vaporizations of carbon and silicon rods in a He carrier gas. The spectra of the Si _nC₁ ^- (3≤n≤7) clusters are similar to those of pure Si_n+1 ^- clusters in the peak positions and their envelopes, which is attributed to the isovalent electronic structure of Si and C atoms as well as to the similar geometrical structure. In contrast, the similarity in the photoelectron spectra is not observed between C_m+1 and Si₁C_m (2≤m≤5) clusters, which is attributed to a change in their geometry; from chain to ring. These experimental conclusions are discussed with the results of our theoretical calculations.