disintegrations

Disintegrations are processes by which a substance breaks apart into smaller components or transforms into different forms. In physics, the term most often refers to radioactive disintegration—the spontaneous transformation of an unstable atomic nucleus into a lighter nucleus, accompanied by emission of particles or electromagnetic radiation.

The principal modes of radioactive disintegration are alpha decay, beta decay (beta minus and beta plus), and gamma emission, along with electron capture. In alpha decay, the nucleus emits a helium-4 nucleus; in beta minus decay, a neutron converts to a proton with emission of an electron and an antineutrino; in beta plus decay, a proton converts to a neutron with emission of a positron and a neutrino; in electron capture, a bound electron is captured by the nucleus, often followed by gamma emission. These processes are probabilistic and characterized by a decay constant λ, with the number of undecayed nuclei N(t) following N(t) = N0 e^(−λt). The half-life t1/2 = ln(2)/λ gives the time scale over which decay occurs.

Nuclei may undergo decay in chains, where a parent nuclide decays to a daughter that is itself unstable, continuing until a stable nuclide is reached. Practical measurements use activity (decays per second) in becquerels or curies, and energies per decay are expressed in electronvolts or megaelectronvolts.

Beyond nuclear contexts, disintegration can describe the breakdown of materials or compounds, such as dissolution in a solvent, fragmentation under stress, or chemical decomposition. In medicine, radiometric dating, diagnostic imaging, and targeted radiotherapy exploit disintegration processes, while safety protocols regulate exposure to ionizing radiation.