Energy-gain-characterized 3D momentum-imaging spectroscopy of N+ ions produced in Arq+ (q=3,8,9,11 and 12) collisions with N2 molecules

The 3D momenta of N+ fragment ions were measured in coincidence with energy-gain-characterized Ar(q-1)+* in electron transfer collisions between Arq+ (q = 3, 8, 9, 11 and 12) and N-2 molecules at 8.0 keV (lab.). The projectile ions scattered within very small angles (less than or equal to0.017degrees) were selectively detected to carry out measurements under the condition that the energy gain became approximately equal to the heat of reaction for the collision system. Main components due to single-electron transfer as well as subcomponents due to transfer ionization of double-, triple- and quadruple-electron transfer processes were observed in the energy gain spectra. It was found that the predissociation from N-2(+) (C (2)Sigma(u)(+) : upsilon' greater than or equal to 3) and direct fragmentations from N-2(2+*) ((1)Pi(u), (1)Delta(g) and (3)Delta(u)) play important roles in the dissociation processes. The electronic state of both the projectile ion and N-2 molecule producedjust after the electron transfer processes were assigned by measuring the heat of reaction.