Nuclear reactions, in which a highly energetic particle (or photon) bits a nucleus and knocks out one or more nucleons or clusters of nucleons, are called ‘spallation’ reactions. The study of spallation reactions, in particular the study of 'excitation functions’ - variation of production cross section with incident energy - is a simple and often very useful means of investigating the mechanism of nuclear reactions. As discussed later, excitation functions for spallation reactions may be divided roughly into two classes, those for which the threshold is in the region where the Bohr compound nucleus mechanism is said to be applicable ( < 50 Mev), and those with the threshold in the Serber knock-on region ( > 50 Mev).

Yaffe, Leo (Supervisor)