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The angle-integrated experimental (p,xn) spectra, fitted with precompound and evaporation spectra from Griffin's statistical model of intermediate structure, produced g, the number of independent-particle states per MeV, and/,., the compound fraction. For 27 A1, 56 Fe, 11B In, and 181 Ta, g increased linearly with A, from 2 to 13, but decreased to 9dbl for 208 Pb, at 18-MeV proton energy E p . At £ p =14 MeV, g=7=bl for 208 Pb, which may signify vanishing shell effects at large E p . Monte Carlo-type intranuclear-cascade-plus-evaporation calculations yielded spectra and cross sections in agreement with the measurements, allowing for several calculational defects that were made obvious in the comparisons. The Monte Carlo calculations yielded f e values close to those derived by fitting the data with Griffin's calculations for targets heavier than 27 A1. "Nuclear temperatures," obtained from LeCouteur's evaporation analysis for multiple-nucleon emissions, agreed for (p,xn) and giant-resonance (y,xn) reactions, both via the intermediate nucleus 209 Bi, but differed considerably for the target 27 A1, where direct and evaporation neutrons are not well separated in mean energy. The three types of analyses utilized here are therefore much more applicable for heavy nuclei than for light. Energy and angle dependence of (y,xn) reactions indicate negligible direct effects, in sharp contrast to (p,xn) reactions, which display a strong forward anisotropy at the high-energy end of the spectra.

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The energy spectra of secondary neutrons in the energy region between 100 and 450 MeV emitted by targets bombarded by 450-MeV protons were measured using a proton-recoil spectrometer. Secondary-proton measurements were also made with this spectrometer. The measurements were made on Be, C, Al, Cu, Co, Pb, and Bi targets and at several angles between 0 and 60 . Two general target thicknesses were employed: thin targets in which the primary beam lost little energy and in which further interaction of the secondary particle was small; and thick targets in which the primary beam lost all or a significant fraction of the initial energy and in which the probability of the secondary particles undergoing further interaction was large. The thin-target results are expressed as cross sections and the thick-target results represent a nucleon transport and are expressed as a yield. A number of comparisons of the cross-section results against the Bertini intranuclear-cascade model indicate reasonable agreement for most secondary-proton data and some secondary-neutron data. In the latter case, the position of the observed quasifree scattering peak is at an unexpectedly low energy.