Separation of ions with the same charge to mass ratio from a collision experiment

Some atomic collision experiments lead to ions having identical q/m ratio, as well as average velocity, so that standard electric and magnetic analyzers are not able to identify them separately. This situation occurs, for instance, in electron interaction with molecular monocations (A2+) producing A22+ (direct ionization) and A+ (dissociation or dissociative ionization). Due to the transfer of internal energy to the kinetic energy of the fragments, they usually have a wider angular and energy distribution in the laboratory frame, compared to direct ionization. By use of a specially designed animated crossed beams apparatus, we are able to separate ionization and dissociation fragments. Here the preliminary results of cross sections measurements for electron impact on the nitrogen monocation, producing N22+ and N+ ions, is reported.