Elastic Scattering of 17-MeV Protons by Heavy Nuclei

Absolute differential cross sections for elastic scattering of protons from ${\mathrm{Ta}}^{181}$, W, ${\mathrm{Pb}}^{208}$, and ${\mathrm{Bi}}^{209}$ have been measured at a center-of-mass energy of 17.00±0.05 MeV at angular intervals of five degrees ranging from 20 to 170°. The estimated relative standard deviation of each point is 3% while the absolute cross-section scale is uncertain by 5% for Pb and Bi and by 10% for Ta and W. The scattered protons were detected by a NaI(Tl) scintillation counter with an over-all energy resolution of 2.5%. Consequently, while all inelastically scattered protons are rejected for Bi and Pb, a small contribution of inelastic protons from the lowest levels in Ta and the tungsten isotopes is included in the measured cross sections. For Ta and W the diffraction pattern appears damped at backward angles relative to the heavier two targets to a greater extent than may be attributed to the effects of an inelastic scattering component.