LASER-INDUCED CLUSTERING DYNAMICS OF [(SIO2)(N)X](-) FROM POROUS SILICA POWDERS

The clustering dynamics of SiO2-containing negative ion clusters gener ated from ultrafine amorphous SiO2 powders with high specific surface area is investigated by XeCl excimer laser ablation time-of-flight mas s spectrometry (TOF-MS). From the evolution of the mass spectra with t he delay time and the number of laser irradiation shots, the key roles played by OH and OH- fragments from the surface silanol groups in the formation of SiO2-containing negative ion clusters are discussed. (C) 1997 Elsevier Science B.V.