Energy partitioning in doubly-charged-ion-neutral charge-transfer processes involving molecular species

Single-electron charge-transfer processes in collisions of molecular doubly charged ions with atoms and molecules were investigated in a series of tra nslational-energy spectroscopy, crossed-beam scattering, and product-lumine scence experiments. The aim of these studies war to determine the partition ing of available energy into the translational, electronic, vibrational, an d rotational energy of the molecular products. The collision energy range i nvestigated was 10-10(3) eV. Those product electronic states were populated with the highest probability for which the translational-energy release wa s about 3-5 eV, indicating that the "reaction window" concept, as derived f rom the Landau-Zener formalism, works well also for molecular systems. At p rojectile kinetic energies in the keV region, populations of the vibrationa l states of the molecular products could be described by the overlap of the respective Franck-Condon factors between the reactant and product states; below 100 eV small deviations were observed. Rotational energy distribution s of the molecular product ions, as determined from the luminescence experi ments, were found to correspond to strikingly low rotational temperatures o f about 400-800 K, i.e., practically to the temperature of the ion source.