Speaker
Description
Half-lives of $N=82$ nuclei below doubly-magic $^{132}$Sn are key input parameters for calculations of any astrophysical $r$-process scenario and play an important role in the formation and shape of the second $r$-process abundance peak. In the past, shell-model calculations of neutron-rich nuclei near the $N=82$ neutron shell closure that are not yet experimentally accessible have been performed by adjusting the quenching of the Gamow-Teller (GT) operator to reproduce the $^{130}$Cd half-life reported in Ref. [1]. The calculated half-lives of other nuclei in the region are known to be systematically too long. Recently, a shorter half-life for $^{130}$Cd was reported [2,3]. A re-scaling of the GT quenching to the new $^{130}$Cd half-life by a constant factor for all nuclei in the region resolved the discrepancy. However, the reduced quenching of the GT operator creates a new discrepancy in the calculated half-life of $^{131}$In. The measurement of $^{131}$In is complicated due to the presence of three known $\beta$-decaying states with roughly the same half-life, making photopeak gating an ideal method to measure each of these half-lives. In this talk, the half-lives of $^{128-130}$Cd and $^{131}$In, as well as the spectroscopy of $^{131}$Sn, measured using the GRIFFIN $\gamma$-ray spectrometer at TRIUMF will be presented.
[1] M. Hannawald et al., Nucl. Phys. A 688, 578 (2001).
[2] R. Dunlop et al., Phys. Rev. C 93, 062801(R)
[3] G. Lorusso et al., Phys. Rev. Lett. 114, 192501 (2015).
