Beta-gamma spectroscopy of the neutron-rich 150Ba

Excited states in the neutron-rich nucleus Ba-150 have been observed via beta-gamma spectroscopy at the Radioactive Isotope Beam Factory, RIKEN Nishina Center. The Ba-150 ions were produced by the in-flight fission of a U-238 beam with an energy of 345 MeV/nucleon. The E(2(+)) energy of Ba-150 was identified at 100 keV, which is the lowest known in the neutron-rich Ba isotopes. A gamma-ray peak was also observed at 597 keV. A mean-field calculation with a fully 3D real space was performed and a static octupole deformation was obtained for the Ba isotopes. K-pi = 0(-) and 1(-) excited states with significant octupole collectivity were newly predicted at around or lower than 1 MeV on the ground state of Ba-150 by a random-phase approximation calculation. The 597 keV gamma ray can be interpreted as a negative-parity state, showing that Ba-150 may possess octupole collectivity.