Kenneth A. Cowen

The importance of high impact parameter interactions in the collision induced dissociation of protonated water clusters by argon using a Wien velocity filter

High impact parameter, i.e., glancing collisions, are of particular interest in ion beam experiments because ions experiencing such collisions remain available in the ion beam for further experiments. The collisional activation and dissociation processes for glancing collisions of protonated water clusters and argon have been studied with a new and simple, single‐stage technique to detect fragment ions using a Wien velocity filter. The technique is specific with regard to the mass of a fragment ion and the mass of the parent from which it originates. A relation is derived and experimentally verified which governs the operation of the device. Absolute values of the attenuation cross section with argon of 11(6), 25(8), 36(11), 47(17), and 66(10) A have been determined for H3O+, H5O2+, H7O3+, H9O4+, and H11O5+, respectively, at beam energies in the range of 300–1000 eV. Absolute values of the glancing collision induced dissociation cross section of 0.62(4), 4.3(1), and 9.1(6) A2 have been determined for the ...

Optimizing internal excitation of H5O2+ in a fast ion beam by glancing collisions with argon: A multiple collision analysis

Abstract Glancing collisions of H 5 O 2 + in a fast ion beam with argon have been shown to impart an average of 1 eV of internal energy to a large fraction of the incident H 5 O 2 + molecules (6.4%) without knocking them out of the beam. Collision-induced dissociation studies have been performed for attenuations of up to 95%. A multiple collision theory is applied to the parent attenuation and fragment appearance data providing a quantitative window on the internal excitation of H 5 O 2 + parent ions. Prospects for detecting infrared emission from molecular ions in this way are discussed.