Electron transfer and bond-forming reactions following collisions of Cl2+ and HCl2+ with CO

Abstract

Collisions between Cl²⁺ and CO have been investigated using time-of-flight mass spectrometry over a collision energy range between 2.2 eV and 7.1 eV in the centre-of-mass frame. The formation of Cl⁺, CO⁺ and C⁺ in electron transfer reactions has been detected and an unusual bond-forming reaction which generates CCl²⁺ has also been observed. The reactive cross-sections, in arbitrary units, for the electron transfer reactions have been evaluated. To extract these cross sections we employ a new method of analysing mass spectral intensities for crossed-beam experiments, an algorithm which allows inter-comparison of the fluxes of all the ionic products from the electron transfer reactions. The observed electron transfer reactivity has been rationalized by calculations based on Landau–Zener theory. To account for the observation of CCl²⁺, we have calculated the relevant energetics showing that the lowest lying doublet state of this dication is bound and is energetically accessible at our collision energies. These energetic arguments indicate that electron transfer in the exit channel between the separating CCl²⁺ and O atom probably forms C⁺ ions via the dissociation of CCl⁺. Additionally, collisions between HCl²⁺ and CO have been studied at collision energies from 2.2 to 7.0 eV in the centre-of-mass frame. In this collision system, proton transfer to form HCO⁺ is observed to compete efficiently with dissociative and non-dissociative electron transfer.