V. Karayonchev

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 , , and 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.

A revised B(E2;2+1

Abstract.The lifetimes of the

\rightarrow

2^+_1

0+1) value in the semi-magic nucleus 210Po

21+ , the

Search for mixed-symmetry states in

2^+_2

^{212}

22+ and the

Po

3^-_1

Evolution of collectivity in the N=100 isotones near Yb170

31- states of 210Po have been measured in the 208Pb(12C,10Be)210Po transfer reaction by the Doppler-shift attenuation method. The result for the lifetime of the

High-spin structures in Xe 132 and Xe 133 and evidence for isomers along the N=79 isotones

2^+_1

Evolution of deformation in neutron-rich Ba isotopes up to A=150

21+ state is about three times shorter than the adopted value. However, the new value still does not allow for a consistent description of the properties of the yrast