Fragments/secondary nuclei

The growth rate of fragments/secondary nuclei immediately after their formation is found to be generally lower than that of a macroscopic unhurt crystal of the same species (Figure 9.14). 

Primary effects comprise recoil of the nucleus and excitation of the electron shell of the atom. The excitation may be due to recoil of the nucleus, change of atomic number Z or emission of electrons from the electron shell. Secondary effects and subsequent reactions depend on the chemical bonds and the state of matter. Chemical bonds may be broken by recoil or excitation. In gases and liquids mainly the bonds in the molecules are affected. The range of recoil atoms is relatively large in gases and relatively small in condensed phases (liquids and solids). Fragments of molecules are mobile in gases and liquids, whereas they may be immobilized in solids on interstitial sites or lattice defects and become mobile if the temperature is increased. 

In a strict sense, spallation is a nuclear fragmentation process in which the target nucleus loses several nucleons. As used in cosmochem-istry, however, the term is used more broadly to designate the product of any nuclear transformation induced by cosmic rays, primary or secondary, whether produced by spallation in the strict sense or by more specific reaction channels involving fewer exiting particles (e.g., (p,pn) or (n, a) reactions). 

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