The phenomena of the deformation was first suggested by Pauli that the hyperfine structure of atomic and molecular energy levels comes from the electromagnetic interaction with nonspherical atomic nuclei. After, N. Bohr in his classic paper on the nuclear liquid drop model in which he introduced the concept of nuclear shape vibrations. If quantum mechanical system is deformed, its spatial density is anisotropic. For deformed system arises because of the symmetry breaking of the nucleus.
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In simple terms, deformation in nuclei seems to be caused by shell effects ( i.e., neutrons and protons move in quantized orbits with non-zero angular momenta, sometimes in pairs due to pairing forces) which produces a cooperative energy that would distort the spherical shape if nuclei were normal liquid drops. Please find further information in the book "The Nuclear Many-Body Problem" by Peter Ring and Peter Schuck, Springer-Verlag, 1980.
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Alexis
Both, Prof Torres and Prof Papakonstantinou are right. Actually surface nucleons moves in a fashion of conglomerate of mosquitoes over the head of a person walking in the park in an odd evening. Each individual mosquito moves independently but tend to maintain the overall shape of the conglomerate. As the man moves the mosquitoes also move with him under a social force which keep them correlated. The nuclear core maintains a spherical or non-spherical shape with a deformation in the outer layer due to the correlated oscillation of surface nucleons which can be well described on the basis of collective model.
Each nucleus is a well defined gird of substructured particles. The same particles you can also find in protons and neutrons. That is why nuclei emit under certain condititions those particles. It's a fetal false conclusion to declaire proton and neutron as part of atomic nuclei.
The "atomic nucleus particle gird" has a well-defined surface, static charge distribution (e.g. quadrupolmoments) and so on. In some cases the particle gird is very symmetrical and for this reason the nucleus is very stable. Here are a few examples: 2-he-4 = tetrahedron, 6-c-12 = icosahedron, 8-o-16 = blunted tetrahedron. The sharpe of nucleus 92-pb-208 is a blunted parallelepiped.
There are not "atomic nuleus shells", and also the atomic nuclei are not spherical or deformed-spherical like the theorie explained.
Deformation in nuclei seems to be caused by shell effects. Yes, i can not agree more!
But, which shells from which shape, and conversely, which shapes from which shells? (Refer to Physica Scripta. Vol. 10A, 53-59, 1974 in attachment).
I think the single-particle levels is the key to this question. The shells are determined by the single-particle levels as well as the shapes. In other words, nucleon-nucleon interaction makes the nuclei deformed.
Basically, in the shell model it is the same as in the atom: nucleons are fermions and must therefore have different quantum Status (or quantum numbers) if they are within the same potential. Only when a shell is completely filled, the overall distribution of electrons/nucleons is spherical.
1) First of all, when we say that a nucleus is not deformed, it means that it has a spherical shape. Therefore a nucleus is said to be deformed when it no longer has spherical symmetry.
2) Experimentally, the nuclear deformation is measured (mainly) by the measurement of the electric quadrupole moment.
3) Theoretically, it is the minimum of the nucleus binding energy as a function of deformation parameters which determines the static equilibrium form of the atomic nucleus.
4) This energy is mainly calculated by the model of the liquid drop to which we add quantum corrections (Strutinsky shell correction and pairing correction) or by a Hatree-Fock model from a phenomenological interaction (there are also other approaches).
5) Essentially, it is the quantum effects (due to the shell structure of nucleons) that are at the origin of nuclear deformation.
6) Nuclear fission is the process of deformation which leads the initial nucleus to a state of two stuck nuclei which detach from each other by Coulomb repulsion.
7) Nuclear deformation is not static. There are generally vibrations and rotations that are superimposed on the static (average) deformation. These vibrations and rotations are due to collective movements of the nucleons.
The theoretical picture of the atomic nucleus allows only their deformation to explain the observed properties (hyperfine structure). Also the quadrupole moments of the atomic nuclei become accessible to an explanation in this way.
If one approaches the structure of the nuclei not on theoretical way like Pauli and Bohr, but on analytical way, they are a spatial particle lattice. As an example, the lattice of the nucleus 28-Ni-62 is given.In the lattice structure of 62 mass particles (pairs of charged pions π+ π-) are embedded 28 charged binding particles (π+ and some K+. The particle numbers can be calculated exactly). No equal distribution of charge is expected in this structure. It also explains the well-defined surface of the atomic nuclei and the explanation of the results of the electron scattering experiments.Thesis The Justification of a realistic Picture of Particles and At...
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