Time-of-flight mass and photoelectron spectroscopy study of LaC n -

Mass spectra of LaC _n ^- were taken by using a laser-vaporization source (LVS) and pulsed arc cluster ion source (PACIS) applied to La-carbon composite rods (1:130 atomic ratio). The mass spectrum using the LVS with annealing procedure has shown several magic numbers for LaC _n ^- (n = 44, 50, 60, and 70), whereas only small LaC _n ^- (up to n = 14) have been observed in the mass spectrum using the PACIS. Photoelectron spectra of some of these have been measured using a magnetic-bottle type time-of-flight electron spectrometer. These results indicate the exsistence of a few conformational isomers for small La-containing carbon cluster negative ions LaC _n ^- (n = 5–8).