nuclear reaction A reaction involving a change in an atomic nucleus, such as fission, fusion, neutron capture, or radioactive decay, as distinct from a chemical reaction, which is limited to changes in the electron structure surrounding the nucleus
photochemical reaction Chemical reaction which is initiated by light of a specific wavelength. In an environmental context an example is the potential action of ultraviolet light on CFCs which may bring about the detrimental degradation of the ozone layer. Photochemical reactions initiate the process of photosynthesis in which plants convert carbon dioxide into sugars, which are incorporated into cell materials
