Alfaemitter

An alpha emitter is a radionuclide that decays by emitting an alpha particle, which is a cluster consisting of two protons and two neutrons (a helium-4 nucleus). In alpha decay, the parent nucleus loses two units of atomic number and four units of mass, producing a lighter, typically more stable daughter nucleus. The released energy for the alpha particle is usually in the range of about 4 to 7 MeV. The decay process is governed by quantum tunneling through the nuclear potential barrier and depends on the specific nuclear structure of the isotope.

Alpha emitters have a very short range in matter; alpha particles are effectively stopped by a sheet of paper or a few centimeters of air, and pose little external hazard. However, if alpha-emitting materials are ingested or inhaled, they can cause significant biological damage due to their high local ionization. Consequently, handling and use rely on sealed sources, containment, and shielding appropriate to the radioisotope.

Common alpha-emitting nuclides include uranium-238, uranium-235, thorium-232, plutonium-239, radium-226, and americium-241. The specific half-life and decay chain determine the long-term radiological characteristics of each emitter. Alpha-emitting isotopes appear in natural decay series and various engineered sources, including medical radiopharmaceuticals and industrial devices.

Applications and measurement: alpha emitters are used in radiometric dating (for example, uranium-lead dating leverages alpha decays in the chain), smoke detectors (americium-241), and certain targeted cancer therapies (such as radium-223 and other alpha-therapy isotopes under development). Detection and quantification are performed by alpha spectrometry, scintillation counters, or semiconductor detectors, with activity expressed in becquerels or curies. Safety regulations govern storage, transport, and disposal of alpha-emitting materials.