Measurement and Calculations of the 39K and 40Ca (n,alpha) Cross Sections at En = 4.5 to 6.5 MeV

Cross sections, angular distributions, and double-differential cross sections were measured for 39K(n.alpha)36Cl reactions at En = 4.5, 5.5. and 6.5 MeV and for 40Ca(n.alpha)37Ar reactions at En = 5.0 to 6.0MeV, using a twin-gridded ionization chamber, and the experimental data were analyzed with the UNF code. The results indicate that the optical model parameters employed in the calculation are appropriate in the energy region. The energy level densities used in our calculations are a little different from the findings of Gilbert and Cameron, and the pair corrections of some nuclei are much smaller than what was determined by them. The. experiment and model calculation results indicate that in the energy region below 7 MeV, the compound nuclear mechanism in predominant; at 6.5 MeV, the preequilibrium emission is ~12%.