β-delayed neutron and γ-ray spectroscopy of $^{17}C$ utilizing spin-polarized $^{17}B$

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