On the quadrupole collectivity in the yrast band of 168Yb

Abstract The lifetimes of eight lower spin levels of the yrast band in 168 Yb, populated via the 154 Sm( 18 O,4n) and 124 Sn( 48 Ca,4n) reactions, were measured, six of them for the first time, by means of the recoil-distance Doppler-shift method. Two versions of the differential decay-curve method have been applied for the data analysis resulting in a very good agreement. The reduced transition probabilities indicate some reduction of the collectivity for states just above the 6 1 + level, i.e. well below the band-crossing. The reasons of this effect are discussed in terms of an interaction between the ground-state band and yet unknown part of the two-quasiparticle ( ν 13 / 2 ) spin-aligned S-band by invoking the shell-structure or alternatively/additionally, as changes in the internal structure/shape induced by the rotation.