DYNAMICS OF THE DISSOCIATION OF THE S-TETRAZINE DICATION PRODUCED BY ONE PHOTON EXCITATION OF THE NEUTRAL MOLECULE

The dissociation of the s-tetrazine dication has been investigated by the photoelectron phototion photoion coincidence method, after photoexcitation in the far ultraviolet (25 to 56 eV) of the neutral molecule. Three body dissociations are found much more abundant than two body ones even close to threshold. From the measurement of kinetic energy release and appearance energies of two body and three body reactions, we find that all channels requires an activation energy. The main three body dissociation processes always involve a N2 ejection. After simulation of the coincidence peak shape, those processes are described by stepwise processes (ejection of a neutral fragment followed by charge separation or the reverse). The intermediate cation (doubly or singly charged) is found either long or short lived compared to its rotational motion. Autoionization of highly excited states of the monocation is suspected to populate the parent dication in rearranged geometry or even in some specific charge separation reactions.