NEAR-THRESHOLD PHOTOIONIZATION TO PROBE NEUTRAL MET-CAR CLUSTERS

Metal-carbon compound clusters of Ti, Zr, V, and Nb are produced by la ser vaporization in a pulsed nozzle cluster source. The distribution o f neutral clusters is investigated by time-of-flight mass spectrometry , with photoionization at a variety of laser wavelengths. Laser wavele ngth and power dependence studies are used to investigate ionization p otentials of different metal-carbon clusters and the role of fragmenta tion in the appearance of mass distributions. The M(8)C(12) met-car cl usters of zirconium, vanadium, and niobium have vertical ionization po tentials greater than 5.76 eV. Ti8C12 has a vertical ionization potent ial of 4.9 + 0.2 eV.