Crystal blocking in heavy ion reactions

The crystal blocking technique for measuring short lifetimes (10-18 s) was developed during the 1960s from the study of the channeling effect. Early blocking lifetime measurements involved light ion resonance reactions yielding typical lifetime values of the order of 10-17 s. Recently, studies on heavy-ion induced fission and fusion have extended the technique into the 10-18 to 10-19 s scale. In this work measurements of fusion for 16O+Ge are presented for bombarding energies around 8 MeV/nucleon. Also measurements of the projectile fragmentation of 44 MeV/ nucleon 40Ar+Ge are discussed. In all reactions studied the presence of particle evaporation is the dominant mechanism that determines the reaction times of ≅ 10-18 s measured with the blocking technique. (orig.)