Abstract
Abstract A new method is presented to measure nuclear reaction times and lifetimes of excited nuclear states from 1 as to 10 fs, based on the blocking effect of charged particles in single crystals. Reaction time measurements are described for the 28Si(p, p')28Si (1.78 MeV, 2+), 70Ge(p, p')70Ge (1.04 MeV, 2+) and 72Ge(p, p')72Ge (0.835 MeV, 2+) reactions at E = 3.61–5.91 MeV. Planar blocking patterns by the (111) crystal plane of thin single crystals were observed for protons scattered at 90° leaving residual nuclei in definite states. Clear reduction of the blocking effect from that of the elastic scattering was found for the 70Ge(p, p')70Ge* and 72Ge(p, p')72Ge* reactions and not for the 28Si(p, p')28Si* reaction. Reaction times τ derived from the reduction were 36±23 and 42±19 as for the 70Ge(p, p')70Ge* and 72Ge(p, p')72Ge* reactions at E = 4.84MeV and τ ≦ 6 as for the 28Si(p, p')28Si* reaction at E = 3.61–5.86MeV.
Published Version
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