Differential cross sections for elastic scattering of neutrons by ${\mathrm{Li}}^6$ and ${\mathrm{Li}}^7$ have been measured in the region of 200- to 600-kev incident energy. The results for ${\mathrm{Li}}^6$ confirm the assignment of $\frac{5}{2^{-}}$ for the 7.46-Mev level in ${\mathrm{Li}}^{7*}$ and indicate that the $s$-wave potential scattering has a statistical channel spin mixture and negative phase shift. Similarly in the case of ${\mathrm{Li}}^7$, the 2.28-Mev level in ${\mathrm{Li}}^{8*}$ is indeed $3^{+}$, the $s$-wave potential scattering has very nearly a statistical channel spin mixture, but the phase shift is positive.

• Received 11 October 1955

DOI:https://doi.org/10.1103/PhysRev.101.765