First $\beta$-decay study with CARIBU and Gammasphere: $^{142,144}$Cs to $^{142,144}$Ba

As part of the commissioning of the CARIBU facility at ATLAS, beams of $^{142}$Cs and $^{144}$Cs ions from CARIBU was charge bred and, subsequently, accelerated to $\sim$6 MeV/A by ATLAS before being transported to the target location of Gammasphere. The $^{142}$Cs beam was implanted in a Pb foil with the rate of $10^3$ ions/s for 16 hours and $\gamma$ radiation following $\beta$ decay (T$_{1/2}$ = 1.68s) was detected by the 101 Compton-suppressed germanium detectors of the Gammasphere array. The power of the CARIBU-Gammasphere combination for $\beta$-decay investigations was demonstrated. The $^{142}$Ba level scheme was considerably expanded: 215 $\gamma$ transitions have been identified and placed into an expanded level scheme with 71 states. Furthermore, a large number of spin-parity assignments were made based on the measured angular correlations. High-precision {\it log ft} values were determined as well. The data provide important new information about the nature of low-spin excitations in this nucleus. In particular, new information is obtained about the strength of octupole correlations and the nature of other low-lying excitations.