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nuclear physics Nuclear physics is the field of physics that studies atomic nuclei and their constituents and interactions, in addition to the study of other forms of nuclear matter. Nuclear physics should not be confused with atomic physics, which studies t ...
, separation energy is the energy needed to remove one
nucleon In physics and chemistry, a nucleon is either a proton or a neutron, considered in its role as a component of an atomic nucleus. The number of nucleons in a nucleus defines the atom's mass number (nucleon number). Until the 1960s, nucleons were ...
(or other specified particle or particles) from an
atomic nucleus The atomic nucleus is the small, dense region consisting of protons and neutrons at the center of an atom, discovered in 1911 by Ernest Rutherford based on the 1909 Geiger–Marsden gold foil experiment. After the discovery of the neutron ...
. The separation energy is different for each nuclide and particle to be removed. Values are stated as "neutron separation energy", "two-neutron separation energy", "proton separation energy", "deuteron separation energy", "alpha separation energy", and so on. The lowest separation energy among stable nuclides is 1.67 MeV, to remove a neutron from beryllium-9. The energy can be added to the nucleus by an incident high-energy
gamma ray A gamma ray, also known as gamma radiation (symbol γ or \gamma), is a penetrating form of electromagnetic radiation arising from the radioactive decay of atomic nuclei. It consists of the shortest wavelength electromagnetic waves, typically ...
. If the energy of the incident photon exceeds the separation energy, a
photodisintegration Photodisintegration (also called phototransmutation, or a photonuclear reaction) is a nuclear process in which an atomic nucleus absorbs a high-energy gamma ray, enters an excited state, and immediately decays by emitting a subatomic particle. The ...
might occur. Energy in excess of the threshold value becomes kinetic energy of the ejected particle. By contrast,
nuclear binding energy Nuclear binding energy in experimental physics is the minimum energy that is required to disassemble the nucleus of an atom into its constituent protons and neutrons, known collectively as nucleons. The binding energy for stable nuclei is alway ...
is the energy needed to completely disassemble a nucleus, or the energy released when a nucleus is assembled from nucleons. It is the sum of multiple separation energies, which should add to the same total regardless of the order of assembly or disassembly.


Physics and chemistry

Electron separation energy or electron binding energy, the energy required to remove one electron from a neutral atom or molecule (or cation) is called
ionization energy Ionization, or Ionisation is the process by which an atom or a molecule acquires a negative or positive charge by gaining or losing electrons, often in conjunction with other chemical changes. The resulting electrically charged atom or molecule ...
. The reaction leads to
photoionization Photoionization is the physical process in which an ion is formed from the interaction of a photon with an atom or molecule. Cross section Not every interaction between a photon and an atom, or molecule, will result in photoionization. The prob ...
,
photodissociation Photodissociation, photolysis, photodecomposition, or photofragmentation is a chemical reaction in which molecules of a chemical compound are broken down by photons. It is defined as the interaction of one or more photons with one target molecule. ...
, the
photoelectric effect The photoelectric effect is the emission of electrons when electromagnetic radiation, such as light, hits a material. Electrons emitted in this manner are called photoelectrons. The phenomenon is studied in condensed matter physics, and solid sta ...
,
photovoltaics Photovoltaics (PV) is the conversion of light into electricity using semiconducting materials that exhibit the photovoltaic effect, a phenomenon studied in physics, photochemistry, and electrochemistry. The photovoltaic effect is commercially ...
, etc.
Bond-dissociation energy The bond-dissociation energy (BDE, ''D''0, or ''DH°'') is one measure of the strength of a chemical bond . It can be defined as the standard enthalpy change when is cleaved by homolysis to give fragments A and B, which are usually radical ...
is the energy required to break one
bond Bond or bonds may refer to: Common meanings * Bond (finance), a type of debt security * Bail bond, a commercial third-party guarantor of surety bonds in the United States * Chemical bond, the attraction of atoms, ions or molecules to form chemical ...
of a molecule or ion, usually separating an atom or atoms.


See also

*
Binding energy In physics and chemistry, binding energy is the smallest amount of energy required to remove a particle from a system of particles or to disassemble a system of particles into individual parts. In the former meaning the term is predominantly use ...


External links

{{Wiktionary
Nucleon separation energies
charts of nuclides showing separation energies Binding energy Nuclear physics