Abstract
We have studied the decay pattern of the state of to probe its quadrupole-octupole coupled two-phonon structure. In particular, a unique fingerprint to prove the two-phonon nature is the decay strength of the transition into the one-octupole-phonon state. -ray spectroscopy was performed after the decay of to obtain the necessary sensitivity for this weak-intensity decay branch. Sufficient amounts of were produced by neutron activation of natural Rb in the TRIGA Mark II reactor. The results show that the value of the transition is equal to the of the transition, directly demonstrating the quadrupole-octupole coupled two-phonon nature of the state. A comparison of the results with energy-density functional plus quasiparticle-phonon model calculations shows remarkable agreement, corroborating this assignment.
- Received 31 August 2023
- Accepted 10 October 2023
DOI:https://doi.org/10.1103/PhysRevC.108.L051301
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