Luminescent observation of multiphoton ionization-fragmentation of chromate ions adsorbed on a disperse SiO2 surface

Direct: evidence for the multiphoton ionization with subsequent fragmentation of the chromate ions (CrO(4)2(-))adsorbed on a disperse SiO2 surface is provided by luminescence measurements using the Nd-doped yttrium aluminum garnet pulsed laser as a source of excitation, Experiments were done with the fundamental laser frequency (lambda = 1.064 mu m; tau(p) = 20 ns). The multiphoton absorption proceeds through an intermediate three-photon resonance state. The luminescence response results from recombination of photoelectrons with ionized CrO42- ions and ionized surface oxygen deficient centers. The dynamics of this process include autoionization, which is stimulated by intermolecular perturbation in overexcited states, fragmentation of chromate ions, and annealing of the oxygen-deficient centers. (C) 1997 American Institute of Physics.