Elastic Scattering of Protons fromLi6Nuclei

Abstract

The differential elastic scattering cross section for protons from ${\mathrm{Li}}^6$ nuclei has been measured for proton energies from 0.45 to 2.9 MeV at six different angles. The scattering data are consistent with an $s$- and $p$-wave phase shift analysis, assuming a single $p$-wave ${\frac{5}{2}}^{-}$ state to be present at about $E_p\left(\mathrm{lab}\right)=1.84\mathrm{}$ MeV, with resonance parameters similar to the parameters previously assigned to the corresponding level in ${\mathrm{Li}}^7$, and a very broad $s$-wave ${\mathrm{½}}^{+}$ state at higher energy. It is also possible to fit the scattering and reaction data with a $p$-wave ${\frac{3}{2}}^{-}$ state and a different choice of $s$-wave background. A $p$-wave ${\mathrm{½}}^{-}$ state is not consistent with the data. No evidence has been found for the existence of a previously reported ${\frac{3}{2}}^{+}$ state near $E_p\left(\mathrm{lab}\right)=1\mathrm{}$ MeV. Removal of the simplifying assumption that only one $p$-wave state is participating would probably lead to different conclusions about the nature of the $s$-wave scattering. The relative stopping cross section for protons in lithium was also measured and found to follow the Bloch formula from 0.8 to 2.8 MeV.