Nuclear reaction cascades

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. 

High-energy cosmic rays, consisting mainly of protons, enter the atmosphere from outer space and initiate a cascade of nuclear reactions, some of which produce neutrons that bombard ordinary N atoms to form C ... 

The process of j3-decay in some respects offers simpler radiochemical consequences than do neutron capture and other reactions, because (a) the nuclear recoil energy is very low and (b) the decay schemes, and thus the probability of Auger cascades, are generally well known. Despite this, no clear mechanisms have been worked out. 

The difficulty in proving the exact nature of prethermal reactions is that they occur too fast for standard solid-state chemical methods. One attractive idea was expressed by Harbottle 29), namely that, if a strong isotope effect is shown, very little subsequent chemical influence can have been felt and the observed species must have been formed by prethermal processes. The supposition here is that isotopic differences come only from differences in the nuclear deexcitation pattern (total energy, y-ray cascades, angular... 

An upper limit can be set to the duration time of several nuclear processes and their consequences such as Auger cascades in the case of electron capture reactions, or the thermal displacement of atoms from one site to another in a-emitting or Coulombic-excitation processes. The subject has recently been reviewed [20]. 

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