The lifetimes of the first excited 2+ and 4+ states in Ni 72 were measured at the National Superconducting Cyclotron Laboratory with the recoil-distance Doppler-shift method, a model-independent probe to obtain the reduced transition probability. Excited states in Ni 72 were populated by the one-proton knockout reaction of an intermediate energy Cu 73 beam. ?-ray-recoil coincidences were detected with the ?-ray tracking array GRETINA and the S800 spectrograph. Our results provide evidence of enhanced transition probability B (E 2; 2+? 0+) as compared to Ni 68, but do not confirm the trend of large B (E 2) values reported in the neighboring isotope Ni 70 obtained from Coulomb excitation measurement. The results are compared to shell model calculations. The lifetime obtained for the excited 4 1+ state is consistent with models showing decay of a seniority ?= 4, 4+ state, which is consistent with the ?
سنة النشـــر