The photoneutron cross section for the ($\gamma , n$) reaction in natural lithium was measured and found to have its maximum at 16.8 Mev, a peak value of 2.3 mb, and a width at half maximum of 9.3 Mev. Fine structure in the region to 10 Mev was resolved as follows: ${\mathrm{Li}}^6(\gamma , np){\mathrm{He}}^4$ threshold at 3.61±0.15 Mev, ${\mathrm{Li}}^6(\gamma , p){\mathrm{He}}^5$ threshold at 4.64±0.08 Mev, a level in ${\mathrm{Li}}^6$ at 5.24±0.05 Mev, ${\mathrm{Li}}^6(\gamma , n){\mathrm{Li}}^5$ threshold at 5.73±0.05 Mev, ${\mathrm{Li}}^7(\gamma , n){\mathrm{Li}}^6$ threshold at 7.30±0.04 Mev, and a level in ${\mathrm{Li}}^7$ at 9.66±0.04 Mev.

• Received 10 February 1958

DOI:https://doi.org/10.1103/PhysRev.110.1123