Spin-parity of the 13.35 MeV state and high-lying states around 20 MeV in excitation energy in 12C nucleus

Abstract

A study of the 11B(3He,d)12C reaction at incident 3He energy Elab = 25 MeV has been performed at the K-130 cyclotron at the University of Jyväskylä, Finland. Differential cross sections have been measured for the 13.35 MeV state and for the states with excitation energy around 20 MeV in 12C. The data were analyzed with the DWBA method. A tentative assignment, 4−, is given for the state at 13.35 MeV in a joint study of the reaction and inelastic scattering of α-particles with the energy of 110 MeV. For the state at 20.98 MeV, the possible spin-parity 3− and the isospin T =0 are assigned for the first time. Our model description of the broad state at 21.6 MeV is consistent with the previous assignments of isospin T = 0 and spin-parity of 2+ or 3−. The excited state at 22.4 MeV may have possible spin-parities of either 6+ or 5−. The collected statistics was insufficient to solve this question. Rotational bands which can exist in 12C were presented.