Electroionization of D2O and H2O and study of fragments H+ and OH+

In the electroionization efficiency curve of H2O and D2O, clearly resolved newly observed structures converging to the (1b2) and (2a1) limits are reported and interpreted between threshold and 31 eV. A perturbation from the OH+ + H + 2e dissociation continuum is observed in the ionization efficiency curve of H2O. Appearance curves of H+ from H2O are analysed and the presence of ion pair formation H+ + OH− at threshold is demonstrated. Observation of these structures reveals new information on the mechanism of electron impact on molecules.