Nuclear structure of low-lying 0+ states in Ge and Se isotopes

The following meanlives of levels in⁷²Se have been measured using the recoildistance Doppler-shift method:Τ(2⁺, 862 keV)=3.1±0.6 ps,Τ(2⁺′, 1317 keV)=12.5±2.6 ps,Τ(4⁺, 1638 keV)=1.2±0.3 ps andΤ(6⁺, 2469 keV)≦0.7 ps. These meanlives yield sixB(E2) values which are discussed together with the known data of the depopulation of the excited 0⁺′ state at 937 keV. Systematics of 0⁺′ states in the mass region 70?A?100 show that the low excitation energy of the 0⁺′ states is correlated with subshell closures. This suggests that the previous interpretation of the 0⁺′ state in⁷²Se as a rotational band head is questionable.