Significant technical advances have been made in the application of the triple-quadrupole double-octopole mass spectrometer for absolute total state-selected cross section measurements of ion-molecule reactions involving O+(4S degree(s), 2D degree(s), 2P degree(s)). By controlling the collision energies for dissociative charge transfer collisions of He+ (Ne+, Ar+) plus O2 in a radio frequency (rf) octopole ion guide gas cell, and by applying appropriate effective ion trapping potentials to the rf octopole ion guide, we have demonstrated that state-selected O+(4S degree(s)), O+(2D degree(s)), and O+(2P degree(s)) reactant ion beams with high purities and usable intensities can be prepared for scattering experiments.
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