State selection of O+(4So,2Do,2Po) using resonance dissociative charge transfer of He+(Ne+, Ar+)+O2 and radio frequency multipole ion guide techniques

By controlling the collision energies for dissociative charge transfer collisions of He+(Ne+,Ar+) +O2 in a rf octopole ion guide gas cell, and by applying appropriate effective ion trapping potentials to the rf octopole ion guide, we show that state-selected O+(4So), O+(2Do), and O+(2Po) reactant ion beams with high purities and usable intensities can be prepared for scattering experiments. This experimental scheme, which makes possible the enrichment of an ionic species with a lower kinetic energy distribution in a rf multipole ion guide, should be useful for state selection of other excited atomic ions by using appropriate dissociative charge transfer or dissociative photoionization processes