Design and performance of a pulse radiolysis system capable of picosecond time resolution.

A unique stroboscopic pulse radiolysis system is described which detects the transient light‐absorbing species formed in solutions by individual fine structure pulses from a 40 MeV linear accelerator. A measured time resolution of 23 psec is attained by using, as the analyzing light, the short (<10 psec) Cerenkov light flashes produced in air by the fine structure pulses of the electron beam. This light is suitably delayed by an optical system in which the path length is slowly changed, then passed through the irradiated sample. The integrated light passing through the sample id detected, and variations in the optical absorption at varying times after the irradiation pulse are observed. The design and performance of the optical, mechanical, and electronic devices which retrieve the absorption signal out of the noise are described in some detail. As an integrated unit, this system meets its expected performance capability, being able to successfully detect absorption signals as small as 0.2%.