Vibrationally Resolved Photoelectron Spectra of TiCx- (x = 2−5) Clusters

Vibrationally resolved photoelectron spectra are obtained for the small TiCx- (x = 2−5) clusters. Adiabatic electron affinities (EAs) and low-lying electronic states are measured for the neutral TiCx clusters. While the EAs are similar for the series of clusters, 1.542 eV for TiC2, 1.561 eV for TiC3, 1.494 eV for TiC4, and 1.748 eV for TiC5, the observed ground-state vibrational frequencies decrease for the larger clusters:  560 cm-1 for TiC2, 650 cm-1 for TiC3, 440 cm-1 for TiC4, and 240 cm-1 for TiC5. The results are interpreted using ring-type structures that are known to be the ground-state structure for similar YCx and LaCx clusters. The current results provide the first and only spectroscopic and electronic information that will be valuable to test future theoretical calculations to understand the detailed structure and bonding of these simple titanium carbon clusters.