Speaker
Description
The triaxial degree of freedom in nuclei has an important role in the shape evolution. The neutron-deficient and neutron-rich Mo isotopes provide a good example. The large collectivity of a neutron-deficient nuclide $^{84}$Mo leads to the isospin-symmetric island of inversion, and the large triaxiality is expected from the state-of-the-art shell model calculation [1]. For the nuclides lying on the neutron-rich side, their low-lying second 2$^{+}$ state is closely related to the triaxiality [2]. The study aimed to perform a detailed spectroscopy for the neutron-rich Mo isotopes $^{112,114}$Mo to understand their triaxial excitations.
The experiment was performed at the RIKEN Nishina Center. We employed the HPGe detector array EURICA to measure the $\beta$-delayed $\gamma$ rays of $^{112,114}$Mo [3]. The $\gamma$-vibrational band has been extended for $^{112}$Mo, and the yrast 2$^+$ and 4$^+$ states were observed for $^{114}$Mo. In the case of $^{114}$Mo, a reduced pairing strength motivated by Ref. [4] implies that an oblate deformation would develop. The new experimental results and the comparison with the five-dimensional collective Hamiltonian calculation will be presented. Moreover, an overview of the shape evolution of the Mo isotopes far from the valley of stability will be given.
References
[1] J. Ha, F. Recchia, S. M. Lenzi, H. Iwasaki, D. D. Dao et al., Nat. Comm. 16, 10631 (2025).
[2] J. Ha, T. Sumikama, F. Browne, N. Hinohara, A. M. Bruce et al., Phys. Rev. C 101, 044311 (2020).
[3] T. Sumikama, J. Ha, F. Browne, N. Hinohara, A. M. Bruce et al., submitted.
[4] M. Yamagami, Y. R. Shimizu and T. Nakatsukasa, Phys. Rev. C 80, 064301 (2009).