Production of water molecules from dissociative recombination of H3O+ with electrons

Water is probably the most important molecule for the thermal properties of dense, interstellar gas, and as such plays a decisive role in establishing the rate at which molecular clouds collapse towards star formation. The synthesis of water is thought to be mainly due to dissociative recombination of H3O+ With electrons,although experiments have, as yet, provided no evidence that H2O is a product of the reaction. Here we present the first observation of water synthesis from the recombination of H3O+, with a branching ratio of 33%. This value is in good agreement with existing observations of the [H2O]/[H3O+] ratio in interstellar clouds.