We have measured total reaction cross sections for 60-MeV protons on ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^{27}{}_{}{}^{}\mathrm{Al}$, ${}_{}{}^{56}{}_{}{}^{}\mathrm{Fe}$, ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$, ${}_{}{}^{59}{}_{}{}^{}\mathrm{Co}$, ${}_{}{}^{60}{}_{}{}^{}\mathrm{Ni}$, ${}_{}{}^{68}{}_{}{}^{}\mathrm{Zn}$, ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}$, ${}_{}{}^{120}{}_{}{}^{}\mathrm{Sn}$, and ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$. We find that, contrary to previous measurements, our results agree with predictions of the optical model. For a fixed-geometry potential the volume absorption term is reasonably constant with $A$, while the surface absorption term increases monotonically from 0.12 MeV for Al to 4.2 MeV for Pb.

• Received 21 April 1969

DOI:https://doi.org/10.1103/PhysRevLett.22.1128