Preference for breaking the O-H bond over the O-D bond following HDO ionization by fast ions

Measurements of the fragmentation of deuterium tagged water molecules, namely HDO, by fast proton and F7+ impact exhibit a very strong isotopic preference for cleavage of the OH bond over the OD bond. Explicitly, the former is about five times more likely than the latter for HDO2+ dissociation. HDO+ exhibits similar behaviour, though the asymmetry is smaller at about a factor of 2. Wave-packet propagation calculations are in good agreement with the measured branching ratio for HDO2+ dissociation.