Reactions of nucleons

The results of some of these experiments are shown in Fig. 7 where the total cross-sections for several typical elements are plotted as a function of energy. 

Weinstein Ann. Progr. Report of Laboratory of Nuclear Science of M.I.T., Cambridge, Mass., May 15, 1955. 

Albert Wattenberg Nuclear Reactions at High Energies. 

The details of the variation with energy of the cross-sections has been of great interest. Hildebrand and Leith (see Table 4) first noted that the cross-sections at 42 Mev did not increase smoothly as Ak Taylor and Wood (Table 4) established by measurements with good energy resolution that there were maxima and minima in the cross-sections below 100 Mev. Specifically, lead had a minimum at about 60 Mev, cadmium and copper had minima in the 30 to 40 Mev range. 

The light nuclei do not have any minima or maxima but just decrease monotonically. 

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Cascade theory and the Monte Carlo method. The general principles of high energy nuclear reactions enumerated by Serber [4] suggests a separation into two phases for the non-elastic reactions of nucleons with a nucleus. The first phase is the rapid development of a nucleonic cascade, and the second phase is the de-excitation of a thermally excited nucleus by the relatively slower process of evaporation. 

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