Low collectivity of the first 2⁺ states of ²¹²,²¹⁰Po

The lifetimes of the first 2⁺ excited states of ²¹²,²¹⁰Po 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.