Scientists refer to atomic nuclei as "quantum many-body systems" because they are formed by many particles (nucleons, which include neutrons and protons) that interact with each other in complex ways. Nuclei can absorb energy, placing them into excited states. These states then lose energy through decay and may emit different particles. The various processes of decay and particle emission are called decay channels. The interplay between the internal characteristics of the excited states and the different decay channels gives rise to interesting phenomena.
