GUIDED-ION BEAM MEASUREMENTS OF THE X++H2O(D2O)(X=AR,N2)

Guided-ion beam cross section and product kinetic energy measurements of charge-transfer and atom-abstraction reactions of the Ar+ + H2O(D2O) and N2+ + H2O(D2O) collision systems are presented for collision energies ranging between 0.2 and 20 eV c.m. Both charge-transfer systems exhibit large hyperthermal cross sections exceeding 10 angstrom2 and are characterized by a long-range interaction, evidenced by the small amount of angular scattering observed in product-ion time-of-flight (TOF) measurements. Weak forward-scattered signals due to orbiting collisions are detected and are interpreted to stem from a dipole orientation that maximizes the long-range attractive forces. The charge-transfer product ion velocity distributions are well described by an osculating complex model. The charge-transfer systems exhibit weak isotope effects that are related to competition with the atom-abstraction channels. The atom-abstraction cross sections represent approximately 10% of the total cross section and the observed distinct isotope effects and TOF distributions are consistent with a pairwise-energy model.