Spectroscopy of 13B via the 13C(t,3He) reaction at 115A MeV

Gamow-Teller and dipole transitions to final states in B-13 were studied via the C-13(t,He-3) reaction at E-t=115A MeV. In addition to the strong Gamow-Teller transition to the B-13 ground state, a weaker Gamow-Teller transition to a state at 3.6 MeV was found. This state was assigned a spin-parity of 3/2(-) by comparison with shell-model calculations using the WBP and WBT interactions which were modified to allow for mixing between nh omega and (n+2)h omega configurations. This assignment agrees with a recent result from a lifetime measurement of excited states in B-13. The shell-model calculations also explained the relatively large spectroscopic strength measured for a low-lying 1/2(+) state at 4.83 MeV in B-13. The cross sections for dipole transitions up to E-x(B-13)=20 MeV excited via the C-13(t,He-3) reaction were also compared with the shell-model calculations. The theoretical cross sections exceeded the data by a factor of about 1.8, which might indicate that the dipole excitations are "quenched". Uncertainties in the reaction calculations complicate that interpretation.