Possible experimental signature of octupole correlations in the 0${}_2^{+}$ states of the actinides

Abstract

$J^{\pi }$= 0${}^{+}$ states have been investigated in the actinide nucleus ${}^{240}$Pu up to an excitation energy of 3 MeV with a high-resolution (p,t) experiment at $E_p$= 24 MeV. To test the recently proposed $J^{\pi }$= 0${}_2^{+}$ double-octupole structure, the phenomenological approach of the spdf-interacting boson model has been chosen. In addition, the total 0${}^{+}$ strength distribution and the $0^{+}$ strength fragmentation have been compared to the model predictions as well as to the previously studied (p,t) reactions in the actinides. The results suggest that the structure of the 0${}_2^{+}$ states in the actinides might be more complex than the usually discussed pairing isomers. Instead, the octupole degree of freedom might contribute significantly. The signature of two close-lying 0${}^{+}$ states below the 2-quasiparticle energy is presented as a possible manifestation of strong octupole correlations in the structure of the 0${}_2^{+}$ states in the actinides.

Comments: 6 pages, 5 figures, published in Phys. Rev. C 88, 041303(R) (2013)