FLUORESCENCE-PHOTOION COINCIDENCE SPECTROSCOPY ON INNER-SHELL EXCITEDMOLECULES

The dissociation processes taking place upon inner shell excitation of small molecules have been investigated by means of coincidence spectr oscopy between a fluorescence photon (260 nm less-than-or-equal-to lam bda(ph) less-than-or-equal-to 600 nm) and one or more photoions. As a complement to the PEPIPICO (photoelectron-photoion-photoion-coincidenc e) experiments, the application of this technique allows to select the dissociation channels leading to an excited, fluorescing electronic s tate and to determine the internal energy and the relative abundance o f excited photofragments. The spectra of N2 and N2O excited in the N 1 s shell and of ICN excited in the I 4d shell have been examined. The i ntensity due to the emission of the parent ion was found to be relativ ely small upon resonant excitation for all three molecules. The excite d fragments (atomic and molecular) comprise the most important part of the collected total fluorescence intensity. The percentage of creatin g an electronically excited state is estimated to be around 5% or less at the investigated excitation energies.