Pulse Radiolysis Studies Using Nanosecond Electron Pulses: Observation of Hydrated Electrons

The design and testing of a pulse radiolysis system with a resolving time of 2.5 nsec is described. This system utilized a 1P28 photomultiplier tube directly coupled to a sampling oscilloscope to attain a rise time of 2.5 nsec. Random shot noise was kept small by using an intense xenon light source, and photomultiplier fatigue was reduced by means of a rotating sector which reduced the average light intensity by 72 times. This system was used in conjunction with a 3-nsec 1.5-amp electron pulse from a 3-MeV Van de Graaff generator. The formation and decay of the solvated electron in water were critically examined. There was no evidence that a delay of greater than 0.5 nsec in the formation of e_ aq⁻ , or that a significant fraction of the solvated electrons showed a nonhomogeneous spur type of decay in times longer than 0.5 nsec.