LASER HEATING OF PHOTOELECTRONS DURING MULTIPHOTON IONIZATION OF MOLECULAR IONS ADSORBED ON DISPERSE SILICA SURFACES

Abstract

The laser heating process of photoelectrons during the multiphoton ionization of the $CrO_{4}^{2-}$ ions adsorbed on a disperse silica ($SiO_{2}$) surface was studied for the first time on the basis of luminescence kinetics measurements carried out by using the fundamental mode of the Nd -doped - yttrium - aluminum -garnet pulsed laser ($\lambda_{exe} = 1.064 \mu m, \tau_{p} = 20 $nc). The luminescence response results from an intrinsic luminescence of the $CRO_{4}^{2-}$ ions excited during recombination process and recombination of photoelectrons with ionized surface oxygen-deficient $centers^{a}$. It has been established that at a fixed multiphoton ionization order there is a time delay ($\Delta \tau$) of the lumincescence response in relation to the excitation pulse and this delay depends on the laser light intensity. In the current presentation an explanation of this phenomenon is given in terms of the laser heating of photoelectrons.