The Lifetime of the Lowest 6⁺ State in ⁵⁴Fe and E2 Effective Charge

抄録

The lifetime of the lowest 6⁺ state in ⁵⁴Fe was measured by the β⁺-γ delayed coincidence method in the decay of the 1.43 min ⁵⁴Co isomer. The half life was determined to be 1.24±0.04 nsec and B(E2: 6⁺→4⁺)=38.9±1.3 e²fm⁴. Assuming pure πf_7⁄2⁻² configuration both for the 6⁺ and 4⁺ states in ⁵⁴Fe, the polarization charge of the 0f_7⁄2 proton (δe_eff) with ⁵⁶Ni as a core is deduced to be 0.9 e. From comparison with theoretical calculations a contribution to δe_eff due to the 2hω excitation of an inert core is found to be nearly the same in ⁴⁸Ca and ⁵⁶Ni.