Giant resonance is a high-frequency collective

excitation Excitation, excite, exciting, or excitement may refer to: * Excitation (magnetic), provided with an electrical generator or alternator * Excite Ballpark, located in San Jose, California * Excite (web portal), web portal owned by IAC * Electron exc ...

atomic nuclei 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 ...

, as a property of many-body quantum systems. In the macroscopic interpretation of such an excitation in terms of an oscillation, the most prominent giant resonance is a collective oscillation of all

proton A proton is a stable subatomic particle, symbol , H+, or 1H+ with a positive electric charge of +1 ''e'' elementary charge. Its mass is slightly less than that of a neutron and 1,836 times the mass of an electron (the proton–electron mass ...

s against all

neutron The neutron is a subatomic particle, symbol or , which has a neutral (not positive or negative) charge, and a mass slightly greater than that of a proton. Protons and neutrons constitute the nuclei of atoms. Since protons and neutrons beh ...

s in a nucleus. In 1947, G. C. Baldwin and G. S. Klaiber observed the giant dipole resonance (GDR) in photonuclear reactions, and in 1972 the giant quadrupole resonance (GQR) was discovered, and in 1977 the giant monopole resonance (GMR) was discovered in medium and heavy nuclei.Chomaz, section 2.2.2.1

Giant dipole resonance

Giant dipole resonances may result in a number of de-excitation events, such as

nuclear fission Nuclear fission is a reaction in which the nucleus of an atom splits into two or more smaller nuclei. The fission process often produces gamma photons, and releases a very large amount of energy even by the energetic standards of radio ...

, emission of neutrons or gamma rays, or combinations of these. Giant dipole resonances can be caused by any mechanism that imparts enough energy to the nucleus. Classical causes are irradiation with

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 ...

s at energies from 7 to 40 MeV, which couple to nuclei and either cause or increase the dipole moment of the nucleus by adding energy that separates charges in the nucleus. The process is the inverse of

gamma decay 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 sh ...

, but the energies involved are typically much larger, and the dipole moments induced are larger than occur in the excited nuclear states that cause the average gamma decay. High energy electrons of >50 MeV may cause the same phenomenon, by coupling to the nucleus via a "virtual gamma photon", in a nuclear reaction that is the inverse (i.e., reverse) of

internal conversion Internal conversion is a non-radioactive, atomic decay process where an excited nucleus interacts electromagnetically with one of the orbital electrons of an atom. This causes the electron to be emitted (ejected) from the atom. Thus, in internal ...

decay.

Giant dipole resonance

See also

References

Further reading

External links