Octupole deformation in $^{144,146}$Ba measured by Coulomb excitation of radioactive beams*

The exotic, neutron-rich $^{144}$Ba ($t_{1/2}$=11.5 s) and $^{146}$Ba ($t_{1/2}$=2.2 s) nuclei are expected to exhibit some of the strongest octupole correlations in A$<$200 systems. Up to now, evidence for such strong octupole correlations has been inferred from observations of low-lying negative-parity states and from the interleaving of positive- and negative-parity levels in the ground-state band. However, the E1 transition strengths are very different in these two nuclei, with two orders of magnitude reduction in $^{146}$Ba. In this experiment, we measure the octupole strength directly by Coulomb excitation of post-accelerated $^{144,146}$Ba beams produced at CARIBU using CHICO2 and GRETINA. In $^{144}$Ba, we found B(E3;3$\rightarrow$0)=48($^{+25}_{-34}$) W.u., a value considerably larger than theoretical predictions, while preliminary results for $^{146}$Ba are also indicative of strong octupole collectivity. The experimental conditions, the analysis, and the results from these challenging new measurements will be presented.