Direct Evidence of Octupole Deformation in Neutron-Rich Ba 144

Abstract

The neutron-rich nucleus Ba144 (t1/2=11.5 s) is expected to exhibit some of the strongest octupole correlations among nuclei with mass numbers A less than 200. Until now, indirect evidence for such strong correlations has been inferred from observations such as enhanced E1 transitions and interleaving positive- and negative-parity levels in the ground-state band. In this experiment, the octupole strength was measured directly by sub-barrier, multistep Coulomb excitation of a post-accelerated 650-MeV Ba144 beam on a 1.0-mg/cm2 Pb208 target. The measured value of the matrix element, 31-M(E3)01+