β-delayed neutron and γ-ray spectroscopy of 17C utilizing spin-polarized 17B.

Excited states in 17C were investigated through the measurement of β-delayed neutrons and γ rays emitted in the β decay of 17B. In the measurement, three negative-parity states and two inconclusive states were identified in 17C above the neutron threshold energy, and seven γ lines were identified in a β-delayed multiple neutron emission of the 17B β decay. From these transitions, the β-decay scheme of 17B was determined. In particular, a de-excitation 1766-keV γ line from the first excited state of 16C was observed in coincidence with the emitted β-delayed neutrons, and this changes the previously reported β-decay scheme of 17B and level structure of 17C. In the present work, the β-NMR technique is combined with the β-delayed particle measurements using a fragmentation-induced spin-polarized 17B beam. This new scheme allows us to determine the spin parity of β-decay feeding excited states based on the difference in the discrete β-decay asymmetry parameters, provided the states are connected through the Gamow-Teller transition. In this work, Iπ=1/2-, 3/2-, and (5/2-) are assigned to the observed states at Ex= 2.71(2), 3.93(2), and 4.05(2) MeV in 17C, respectively. [ABSTRACT FROM AUTHOR]