Intramolecular isotope effects in the bond-forming reaction of CF22+ with HD

The relative yield of the molecular ions (HCF2+ and DCF2+) produced by the bond-forming reaction between HD and CF22+ has been determined as a function of the collision energy from 0.17 to 0.62 eV in the centre-of-mass frame. At low collision energies, this chemical reaction exhibits an intramolecular isotope effect favouring the formation of DCF2+. This isotope effect increases in strength with decreasing collision energy and at the lowest collision energies we detect approximately twice as many DCF2+ as HCF2+ ions. One possible explanation of this observation is that electron transfer precedes the bond-forming step of the chemical reaction.