Crystal blocking in heavy ion reactions

The crystal blocking technique, used to measure very short lifetime (10-18 sec), was developed during the 1960's primarily in connection with the study of the channeling effect. Early blocking lifetime measurements involved light ion resonance reactions yielding typical lifetime values down to the order of 10-17 sec. Recently, studies of heavy-ion induced fission and fusion have extended the technique into the 10-18 to 10-19 sec scale. In this work measurements of fusion for 16O + Ge and deep inelastic reactions for 28Si + Ge are presented for bombarding energies around 8 nucleon. Also measurements of the projectile fragmenatation 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 about 10-18 sec extracted with the blocking technique. 16 refs., 9 figs