Electron Volts can be used to express the energy of particles other than electrons, for example, neutrons, bowling balls, and satellites. EV's can also be converted to velocity. It may be that a charged water molecule, traveling with a velocity which matches one of Stan's photoelectron values, would produce the impact dissociation. If this velocity is less than the speed of sound in water, then that could be the key to resonance.
Here's a link to a conversion calculator:
http://www.calctool.org/CALC/phys/newtonian/k_energy
