On the structure of negative-parity states in 66Zn and 70Ge

Abstract Mean lifetimes of negative-parity states in 66 Zn and 70 Ge have been measured using the recoil distance Doppler shift technique. The states in 66 Zn have been studied through the reaction 55 Mn( 14 N, 2pnγ) 66 Zn at E = 47 MeV, those in 70 Ge through the reaction 56 Fe( 16 O, 2pγ) 70 Ge at E = 46 MeV. The measurements were performed with a plunger apparatus with a piezo-electric distance regulation. The mean lifetimes in 66 Zn were measured to be 66 ± 4ps (5 − state), 43 ± 2 ps (6 − state), 192 ± 15 ps (7 − state), and 2.7 ± 1.2 ps (9 − state), those of 70 Ge 19.7 ± 2 ps (5 − state), 51 ± 4 ps (6 − state), and 25.2 ± 1.4 ps (7 − state). Deduced B ( Ml ) and B ( E 2) values are compared with theoretical predictions of a two-proton cluster-vibration coupling model (CVM) which describes these states as couplings of g 9 2 ⊗ (fp shell) proton clusters to zero, one and higher phonon excitations of the corresponding Ni and Zn cores. Good overall agreement between the theoretical values and the experimental data was found.