Alpha-Particle Reaction Cross Sections at 40 MeV

Abstract

We have measured the nonelastic cross section ${\ensuremath{\sigma}}_{R}$ for 40-MeV alpha particle for 19 target elements ranging in atomic, weight $A$ between 9 and 232. The results have been compared with the predictions of the optical model ${\ensuremath{\sigma}}_{I}$. The ratio $\frac{{\ensuremath{\sigma}}_{R}}{{\ensuremath{\sigma}}_{I}}$ deviates from unity in a systematic fashion being less than 1 for the lightest elements and greater than 1 for the heaviest. Superimposed on this trend, $\frac{{\ensuremath{\sigma}}_{R}}{{\ensuremath{\sigma}}_{I}}$ dips by 18% for elements where the nuclear charge is near 28. A similar effect had been noted earlier in proton-reaction cross-section data but not in deuteron-reaction cross-section data.