Elastic scattering cross sections for Li-6 and Li-7 scattering by aluminum, silicon and titanium below 12 MeV at angles of 140 degrees and 170 degrees

Elastic scattering cross sections for Li-6 and Li-7 scattering by natural a luminum, silicon and titanium have been measured in the energy range of 4-1 1 MeV. Scattering angles were 140 degrees and 170 degrees for Li-6 and 140 degrees for Li-7. The threshold energies above which Rutherford backscatter ing becomes invalid have been determined. Above this threshold the cross se ctions decrease rapidly, rendering backscattering analysis impractical. For Li-7 scattering by Al and Si the observed threshold values were higher tha n for Li-6 scattering. This behavior was reversed for scattering by Ti. The findings were systematic for both scattering angles. The present cross sec tion and threshold data have been compared with the available literature da ta. The experimental threshold energies are compared with results obtained by analytical models based on nuclear potential perturbation calculations. For all targets studied, the experimental Li-6 threshold energy values exce ed the calculations. In the case of Li-7 the comparison yields less systema tic results. (C) 1999 Elsevier Science B.V. All rights reserved.