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A method for determining the cross section for compound-nucleus formation, σCN, in nuclear reactions initiated by protons of energy in the range 20–100 MeV is proposed. The method is based on measuring cross sections for the yield of isotopes maximally remote from the target nucleus. The applicability of the method is illustrated by applying it to the reaction 209Bi(p, xn), which is considered by way of example. Data obtained for the cross section σCN are compared with the results of calculations performed on the basis of the intranuclear-cascade model.

Systematics is proposed for determining the isomeric ratios (and, consequently, the production cross sections) for high-spin isomeric states in nuclear reactions induced by intermediate-energy protons. It is based on experimental data obtained by bombarding tantalum targets with protons of energy 100 to 500 MeV. For reactions involving the emission of more than two nucleons, a linear dependence between the spin transfer and the logarithm of the isomeric ratio is observed; i.e., {sigma}{sub m}/{sigma}{sub g}{approx}aexp[-b|J{sub m}-J|] where {sigma}{sub g} is the cross section for the ground state (perhaps from a calculation within the intranuclear cascade-evaporation model); {sigma}{sub m} is the cross section for the isomeric state of the nucleus; J{sub m} and J{sub t} are spin values for, respectively, the product isomeric nucleus and the target nucleus; and a and b are coefficients that are determined from 16 experimental results (a {approx} 1.05, b {approx} 0.47). The systematics is assumed to be valid over a wide range of nuclei, proton energies, and isomeric ratio. An explanation for the observed regularities is given.

For the nuclear-fission process induced by photons of energy in the range 150 < E γ < 600 MeV and accompanied by pion emission, the total cross section; the angular and differential distributions of pions; the excitation-energy, mass, and charge distributions of compound nuclei; and the mass distribution of the fission fragments are predicted on the basis of the cascade-evaporation-fission model. These features are compared for the cases of nuclear fission induced by photons and protons of initial energy in the same range.

Basic features of the nuclear-fission process induced by protons of incident energy in the range 150

The production of Λ hyperons in π+A interactions is studied on the basis of the intranuclear-cascade model, and the excitation-energy, momentum, angular-momentum, charge, and mass distributions of the ensemble of product hypernuclei are determined. The decay of excited hypernuclei via particle emission and fission is considered. It is shown that, for the production of heavy Λ hypernuclei, the optimal momentum of the incident π+ meson is about 1 GeV/c. The cross section of the channel in which heavy-nucleus decay induced by a π+ meson is accompanied by the emission of a K+ meson is estimated, and it is proposed to use the reaction (π+, K+f) in measurements of the fission barrier in hypernuclei and of their level density.