Search for Gamow-Teller strength in the continuum via the He3(n,p)3H reaction at 288 MeV

Cross sections for the He3(n,p) reaction were measured at angles of 2.7°, 7.5°, 14.4°, 28.2°, and 34.9°(c.m.) at an incident beam energy of 288 MeV. Outgoing protons were observed to energies corresponding to a Q value of -40 MeV. The reduced cross section for the Gamow-Teller component of the ground-state isobaric-analog transition was determined to be σ^=σ(q=0)/BGT=6.9±0.2 mb/sr. This value is significantly smaller than that observed for nuclei in the mass range 6≤A≤13. A multipole analysis of the data indicates that the cross section of the continuum up to a Q value of -20 MeV involves mainly ΔL=1 spin dipole transitions. The analysis determines an upper limit of 0.06 units of Gamow-Teller strength in transitions to excited states between 7 and 16 MeV, but is consistent with no Gamow-Teller strength in this region. Distorted wave impulse approximation calculations using transition amplitudes from a large-scale shell model calculation provide a good fit to the measured ground-state cross section, but fail to account for the magnitude of the measured cross sections to the continuum below 30 MeV excitation.