Double ionization of water molecule induced by swift H⁺

Experimental cross sections for single and double ionization of H₂O by swift H⁺ with energy ranging from 0.5 to 2.0 MeV are reported. In this energy range the ionization is the dominant collision process and charge transfer reactions can be disregarded. A multi-hit coincidence technique was used to measure the H⁺ + OH⁺ and H⁺ + O⁺ fragmentation channels. A model calculation allowed us to separate the post collisional contribution from the direct double ionization process, whenever an electron vacancy occurs in the 2a1 molecular orbital. (paper)