Interacting boson model

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The interacting boson model (IBM) is a model in nuclear physics in which nucleons (protons or neutrons) pair up, essentially acting as a single particle with boson properties, with integral spin of 0, 2 or 4.

Nuclear physics field of physics that deals with the structure and behavior of atomic nuclei

Nuclear physics is the field of physics that studies atomic nuclei and their constituents and interactions. Other forms of nuclear matter are also studied. Nuclear physics should not be confused with atomic physics, which studies the atom as a whole, including its electrons.

Proton nucleon (constituent of the nucleus of the atom) that has positive electric charge; symbol p

A proton is a subatomic particle, symbol
, with a positive electric charge of +1e elementary charge and a mass slightly less than that of a neutron. Protons and neutrons, each with masses of approximately one atomic mass unit, are collectively referred to as "nucleons".

Neutron nucleon (constituent of the nucleus of the atom) that has neutral electric charge (no charge); symbol n

The neutron is a subatomic particle, symbol
, with no net electric charge and a mass slightly larger than that of a proton. Protons and neutrons constitute the nuclei of atoms. Since protons and neutrons behave similarly within the nucleus, and each has a mass of approximately one atomic mass unit, they are both referred to as nucleons. Their properties and interactions are described by nuclear physics.


It is sometimes known as the Interacting boson approximation (IBA). [1] :7

The IBM1/IBM-I model treats both types of nucleons the same and considers only pairs of nucleons coupled to total angular momentum 0 and 2, called respectively, s and d bosons.

Nucleon particle that makes up the atomic nucleus (proton or neutron)

In chemistry and physics, 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 an isotope's mass number.

In quantum mechanics, a boson is a particle that follows Bose–Einstein statistics. Bosons make up one of the two classes of particles, the other being fermions. The name boson was coined by Paul Dirac to commemorate the contribution of Indian physicist and professor of physics at University of Calcutta and at University of Dhaka, Satyendra Nath Bose in developing, with Albert Einstein, Bose–Einstein statistics—which theorizes the characteristics of elementary particles.

The IBM2/IBM-II model treats protons and neutrons separately.

Both models are restricted to nuclei with even numbers of protons and neutrons. [1] :9

Regions of differently shaped nuclei, as predicted by the Interacting Boson Approximation IBA nuclear shells.svg
Regions of differently shaped nuclei, as predicted by the Interacting Boson Approximation

The model can be used to predict vibrational and rotational modes of non-spherical nuclei. [2]


This model was invented by Akito Arima and Francesco Iachello in 1974. [1] :6

See also

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In particle physics, the strong interaction is the mechanism responsible for the strong nuclear force (also called the strong force, nuclear strong force, or colour force), and is one of the four known fundamental interactions, with the others being electromagnetism, the weak interaction, and gravitation. At the range of 10−15 m (1 femtometer), the strong force is approximately 137 times as strong as electromagnetism, a million times as strong as the weak interaction, and 1038 times as strong as gravitation. The strong nuclear force holds most ordinary matter together because it confines quarks into hadron particles such as the proton and neutron. In addition, the strong force binds neutrons and protons to create atomic nuclei. Most of the mass of a common proton or neutron is the result of the strong force field energy; the individual quarks provide only about 1% of the mass of a proton.

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Subatomic particle particle whose size or mass is less than that of the atom, or of which the atom is composed; small quantum particle

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Magic number (physics) number of protons or neutrons that make a nucleus particularly stable

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Helium-4 isotope of helium

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Semi-empirical mass formula Formula to approximate nuclear mass based on nucleon counts

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Nuclear binding energy energy required to split a nucleus of an atom into its component parts.

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Nuclear structure

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Nuclear matter

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Igal Talmi Israeli nuclear physicist

Igal Talmi is an Israeli nuclear physicist.

Atomic nucleus core of the atom; composed of bound nucleons (protons and neutrons)

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 in 1932, models for a nucleus composed of protons and neutrons were quickly developed by Dmitri Ivanenko and Werner Heisenberg. An atom is composed of a positively-charged nucleus, with a cloud of negatively-charged electrons surrounding it, bound together by electrostatic force. Almost all of the mass of an atom is located in the nucleus, with a very small contribution from the electron cloud. Protons and neutrons are bound together to form a nucleus by the nuclear force.

Nuclear drip line boundary on the periodic table demarcating where atomic nuclei decay by emitting protons or neutrons

The nuclear drip line is the boundary delimiting the zone beyond which atomic nuclei decay by the emission of a proton or neutron.

Akito Arima Japanese politician

Akito Arima is a Japanese nuclear physicist, known for the interacting boson model.

Francesco Iachello is an Italian theoretical physicist and engineer, who works mainly on nuclear and molecular physics. He and his collaborator Akito Arima are the creators of the "interacting boson model".

History of subatomic physics

The idea that matter consists of smaller particles and that there exists a limited number of sorts of primary, smallest particles in nature has existed in natural philosophy at least since the 6th century BC. Such ideas gained physical credibility beginning in the 19th century, but the concept of "elementary particle" underwent some changes in its meaning: notably, modern physics no longer deems elementary particles indestructible. Even elementary particles can decay or collide destructively; they can cease to exist and create (other) particles in result.


  1. 1 2 3 Walter Pfeifer (1998). An Introduction to the Interacting Boson Model of the Atomic Nucleus (PDF). ISBN   978-3-7281-2520-0.
  2. 1 2 Kratz, J. V. (5 September 2011). The Impact of Superheavy Elements on the Chemical and Physical Sciences (PDF). 4th International Conference on the Chemistry and Physics of the Transactinide Elements. Retrieved 27 August 2013.

Further reading