Measurement of the Li-7(gamma, t)(4) He ground-state cross section between E-gamma=4.4 and 10 MeV

The Li-7(gamma, t)(4) He ground state cross section was measured for the first time using monoenergetic gamma rays with energies between 4.4 and 10 MeV at the High Intensity Gamma-ray Source. The reaction is important for the primordial Li problem and for testing our understanding of the mirror a-capture reactions H-3(alpha, gamma)(7) Li and He-3(alpha, gamma)(7) Be. Although over the last 30 years most measurements of the H-3(alpha, gamma)(7) Li reaction have concentrated in an energy range below E gamma = 3.65 MeV, measurements at higher energies could potentially restrict the extrapolation to astrophysically important energies. The experimental arrangement for measuring the Li-7(gamma, t)He-4 reaction included a large-area silicon detector array and several beam characterization instruments. The experimental astrophysical S factor of H-3(alpha, gamma) calculated from the present data was fitted using the R-matrix formalism. The results are in disagreement with previous experimental measurements in the same energy range but the extrapolated S factor agrees with the potential model calculation and lower energy experimental data.