Collision-Induced Dissociation of D2+ Ions by Argon and Nitrogen

Abstract

The reactions D₂⁺+X→D⁺+D+X, where X is Ar or N₂, have been studied with an angular ion‐scattering apparatus at ion laboratory energies in the range 5–120 eV. Kinetic‐energy distributions as well as angular distributions of the product D⁺ ions have been determined. The experimental method consists of directing a well‐collimated, mass‐analyzed, and energy‐selected ion beam into a scattering region and analyzing the product ions with a 127° electrostatic velocity selector and a radio‐frequency mass filter. The product ion analysis and detection system rotates about the center of the scattering region. The results are discussed in terms of a simple two‐step collision model, where the D₂⁺ ion is first excited electronically to the antibonding ²Σ_u state, and then dissociates. The possibility of direct excitation of the D₂⁺ ion into the vibrational continuum is also discussed. If either model is assumed for the reaction, the experimental results indicate that the most probable reaction channel for the collision‐induced dissociation reaction is one in which primary D₂⁺ ions with large vibrational energies give rise to D and D⁺ products which separate with small relative velocities. These results are consistent with some existing opinion that the collision‐induced dissociation cross section increases rapidly as the vibrational excitation of the primary ion is increased.