Shape evolution of neutron-rich <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mmultiscripts><mml:mi>Mo</mml:mi><mml:mprescripts/><mml:none/><mml:mrow><mml:mn>106</mml:mn><mml:mo>,</mml:mo><mml:mn>108</mml:mn><mml:mo>,</mml:mo><mml:mn>110</mml:mn></mml:mrow></mml:mmultiscripts></mml:math> isotopes in the triaxial degree of freedom
J. Ha, T. Sumikama, F. Browne, Nobuo Hinohara, A. M. Bruce, S. Choi, I. Nishizuka, S. Nishimura, P. Doornenbal, G. Lorusso, P.-A. Söderström, H. Watanabe, R. Daido, Z. Patel, S. Rice, L. Sinclair, J. Wu, Z. Y. Xu, A. Yagi, H. Baba, N. Chiga, R. Carroll, F. Didierjean, Y. Fang, N. Fukuda, G. Gey, E. Ideguchi, N. Inabe, T. Isobe, D. Kameda, I. Kojouharov, N. Kurz, T. Kubo, S. Lalkovski, Z. Li, R. Lozeva, H. Nıshıbata, A. Odahara, Zs. Podolyák, P. H. Regan, O. J. Roberts, H. Sakuraï, H. Schaffner, G. S. Simpson, Hiroaki Suzuki, H. Takeda, M. Tanaka, J. Taprogge, V. Werner, O. Wieland
Abstract
Background: Neutron-rich nuclei with mass number between 100 and 110 attract much attention, since several kinds of shapes, such as spherical, prolate, oblate, and triaxial shapes, are predicted. In particular, for neutronrich Mo isotopes, different models predict different magnitudes and rigidity of triaxial deformation. Previous interpretations of experimental results based solely on low-lying 2 + 2 states are insufficient to distinguish between the rigid triaxial shape, vibration, or -soft rotor. Purpose: The shape evolution of 106 Mo, 108 Mo, and 110 Mo is investigated through their 2 + 1 -state lifetimes, decay-branching ratios of the 2 + 2 state, and energies of the low-lying collective excited states with K = 0 + , 2 + , and 4 + . Method: -delayed -ray spectroscopy was employed for neutron-rich Nb and Zr isotopes produced at the RIKEN RI Beam Factory to populate excited states in 106 Mo, 108 Mo, and 110 Mo. The EUroball-RIKEN Cluster Array was used for high-resolution -ray detection and lifetimes of the 2 + 1 states were determined using the UK fast-timing array of LaBr 3 (Ce) detectors.