Kinematic investigations of ion-neutral collision mechanisms at ≈ 1 eV

Abstract

A new pulsing technique is described for the study of ion-neutral collision processes at energies of ≈ 1 eV. Short, high voltage pulses applied to the repeller plate of a mass-spectrometer ion source can produce reactant ion beams of constant velocity. Velocity analysis of both reactant and product ions is achieved through pulsed de-focusing of the ion beam, using a time-of-flight technique.

The collision mechanisms of the reactions CD⁺₄+ CD₄→CD⁺₅+ CD₃ HD⁺+ HD[graphic omitted], are shown to involve complex formation at lab. energies of 1·7 and 0·36 eV respectively. The following non-reactive collision processes have been studied: He⁺+ H₂→He⁺+ H₂, C₂H⁺₄+ C₂H₆→C₂H⁺₄+ C₂H₆

The latter forms a complex which dissociates to give back the original reactants whereas the former does not proceed via a complex. This is explained by the inability of the former system to convert relative translational energy into internal energy of the complex. For the latter process, this conversion is very much easier.