Inelastic Proton Scattering in Medium-Weight Elements

Abstract

Measurements were made of the energy distribution of emitted protons from nuclear reactions induced by protons of various energies between 11 and 23 Mev in elements of atomic number 22 to 30. At intermediate energies, the spectrum shows two maxima; there is strong evidence that the low-energy maximum is due either to "second protons," or to simultaneous emission of two particles. Measurements of nuclear temperatures at 18 Mev are strongly distorted by these effects. At lower bombarding energies, the low-energy contribution may be subtracted off, and distortion of the high-energy part of the spectra by direct ejection is not large, so that the statistical theory of nuclear reactions may be studied. Values obtained for the level density parameter $a$ are independent of the energy of the emitted particle, independent of bombarding energy, slowly varying with atomic weight, and consistent with values obtained from neutron-induced reactions. But when these values are used to calculate cross sections for ($n, p$) and ($p, p^{\prime }$) reactions, it is found that protons are emitted with excessive probability in the latter. Some possible explanations for this are discussed.