Intrinsic electric quadrupole moment of the Kπ=8- isomeric state in 178Hf

The lifetime of the 9- state in the rotational band based on the 4.0 s, K-pi = 8(-), isomeric state (Hf-178(1)m) from the decay of the 31-yr isomer (Hf-178(m2)) was determined to be 99(2) ps by means of the fast-timing technique using two LaBr3(Ce) scintillators. The d(E2/M1) mixing ratios of the Delta I = 1 gamma rays depopulating levels in this band were deduced from gamma-gamma angular correlations by using a Hf-178(m2) radioactive source located at the center of the Gammasphere HPGe detector array. The new results, together with previous spectroscopic information, provide a different way to extract the intrinsic quadrupole moment of Q(0) = 6.45(14) eb for the Hf-178(m1) band. A possible explanation for the reduction of the Hf-178(m1) nuclear charge radius is presented.