Spin-parity assignments in 15C* by a new method: β-delayed spectroscopy for a spin-polarized nucleus

We propose a method of spin-parity assignments in decay spectroscopy. Its feasibility was tested for the beta-delayed neutron decay of spin-polarized B-15. The beta-decay asymmetries were measured in coincidence with the delayed neutrons, and the AP values were evaluated for five allowed transitions leading to the excited states in C-15 (E-x=3.103, 4.220, 4.657, 5.866, and 6.426 MeV). The spin parities of the former three states were uniquely assigned as 1/2(-), 5/2(-), and 3/2(-), respectively. These assignments are consistent with the previous assignments. Because of insufficient statistics for the 5.866-MeV state (1/2(-)), an incorrect assignment (3/2(-)) could not be excluded within the 1sigma deviation. The spin-parity of the 6.417-MeV state is suggested to be 1/2(-). The peak analysis with detector response in the neutron time of flight spectra enabled precise determinations of the level energies and widths. The level widths were determined for the first time. The present method is also applicable for beta-delayed proton, alpha, and gamma decays, and it can be a powerful tool for spectroscopic studies of nuclei far from the stability.