Elastic-scattering experiments have been performed with ${\mathrm{Li}}^6$ on ${\mathrm{Li}}^6$ from 3.2 to 7.0 MeV and with ${\mathrm{Li}}^7$ on ${\mathrm{Li}}^7$ from 4.0 to 6.5 MeV. In the lower portion of this energy range the observations follow Mott's scattering formula but at higher energies fall below these predictions. An analysis of the data in terms of the rounded-cutoff Blair model resulted in a set of parameters which was not sharply defined and probably not unique but which gave curves which reproduced satisfactorily the fluctuations of cross section with angle. An analysis in terms of one parameter, the interaction distance, gave values of $r_0=(1.38\mathrm{}\pm 0.03)\times {10}^{-3\mathrm{}}$ cm for ${\mathrm{Li}}^6$ and $r_0=(1.52\mathrm{}\pm 0.03)\times {10}^{-13\mathrm{}}$ cm for ${\mathrm{Li}}^7$.

• Received 3 September 1965

DOI:https://doi.org/10.1103/PhysRev.141.961