Excitations from dissociative fragments produced in H++H2O collisions

We report on photon emissions in the 200-800 nm region resulting from collisions of 200 keV protons with H2O. The most prominent features observed in the spectrum are the Balmer series of hydrogen and two OH molecular bands. Several less intense O+ as well as neutral O lines are also observed. The absolute photon emission cross sections of the major lines and bands were measured. The results indicate that a primary dissociation pathway involves the formation of H2O+ by removing a 1b(2) electron. The unstable H2O+ ion further dissociates into H++OH or OH++H. The dominant presence of neutral hydrogen lines and O+ lines leads to the conclusion that the subsequent dissociation of OH+ into H+O+ prevails over the other possible dissociation pathway leading to H+ and neutral oxygen fragments.