Proton total reaction cross sections (σR) have been measured for 51V, 54Fe, 56Fe, 57Fe, and 59Co at seven incident proton energies between 20.8 and 47.8 MeV at the University of Manitoba's Cyclotron Laboratory. Our results are compared with an optical-model analysis using global parameters. In general, the predicted total reaction cross sections agree quite well with the measured values. Nuclear transparency calculations have been made for these nuclei using all existing data between 8 and 100 MeV, and nuclei are found to be most reactive between 10 and 25 MeV, with nuclei becoming increasingly transparent as the incident proton energy increases above about 25 MeV. Using previously measured data from Si to 68Zn, along with the current measurements, we observe that when nuclear size effects are removed, the reaction cross section shows departures from average behavior near shell closings corresponding to N or Z values of 20 and 28.
Theoretical reaction cross sections for alpha particles with an optical model