Photoelectron spectroscopy of silicon-carbon cluster anions

Photoelectron spectra of C_nSi_m^- cluster anions (3≤ n, m ≤6) were measured at the photon energy of 3.49 eV, by using a magnetic-bottle electron spectrometer having ∼60-meV resolution. The C_nSi_m^- clusters were produced by laser vaporization of a carbon-silicon mixture rod in a He carrier gas. The spectra of the C₁Si_m-1^- clusters are similar to those of pure Si^-_m clusters in the peak positions and their envelopes, which is attributed to the similarity in electronic structure of Si and C atoms, leading to a similar geometry. In contrast, the similarity in the photoelectron spectra is not observed between C^-_n and C_n-1Si₁^- clusters, which is attributed to a change in their geometry; from chain to ring.