FLUORESCENCE-PHOTOION COINCIDENCE SPECTROSCOPY ON INNER-SHELL EXCITED MOLECULES

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