Low collectivity of the first 2+ states of ²¹²Po,²¹0Po
The lifetimes of the first 2+ excited states of ²¹²Po,²¹0Po were measured in two transfer reactions ²08Pb(¹²C,8Be)²¹²Po and ²08Pb(¹²C,¹0Be)²¹0Po by the Recoil Distance Doppler Shift (RDDS) method and by the Doppler Shift Attenuation method (DSAM), respectively. The derived absolute B(E2) values of 2.6(3) W.u. for ²¹²Po and 1.83(28) W.u. for ²¹0Po indicate low collectivity. It is shown that the properties of the yrast 21+, 41+, 61+ and 81+ states in both nuclei cannot be described consistently in the framework of nuclear shell models. It is also demonstrated in the case of ²¹0Po that Quasi-particle Phonon Model (QPM) calculations cannot overcome this problem thus indicating the existence of a peculiarity which is neglected in both theoretical approaches.
Cortés, Martha Liliana
Institut für Kernphysik, Technische Universität Darmstadt, Darmstadt, Germany