A folding model for crystal defects in the shape analysis of blocking lifetime measurements

A new method of analysis is presented for experiments that measure nuclear reaction times exploiting the blocking effect in single-crystals. It is based upon a direct comparison between measured and calculated blocking patterns, obtained by folding the angular distribution for perfect crystals with a function describing the influence of the defects. Such a function is found by comparing measured and calculated "prompt" patterns. The resulting equations are solved using Tikhonov's regularization procedure. The whole method is applied to a reanalysis of an earlier series of results on the ²⁷Al (p, α ₀) resonance at E_p=632.2 keV. The resulting lifetime of the ²⁸Si 12.195 MeV level, τ = (85.3 ± 5.3) as, agrees with that deduced from resonance reaction yields, and is somewhat different from an earlier analysis based on the filling-in parameter R.