NANOSECOND AND PICOSECOND LASER-DESORPTION OF C-60

Laser desorption of C-60 using nanosecond and picosecond laser pulses has been investigated. The velocity distributions of the desorbed ions were determined by means of time-of-flight mass spectrometry. Optical emission spectroscopy was used to determine the internal energy of th e desorbed species. Typically, the C-60(+) velocity distributions are bimodal, indicative of two distinct desorption mechanisms. The velocit ies and internal energies of the slow particles are consistent with a purely thermal desorption mechanism. The fast particles, which dominat e for desorption with ps pulses, cannot be produced by a purely therma l mechanism. Different mechanisms are postulated for the production of the fast components in the two cases.