Jul 21, 2020
The combination of the AGATA multi-detector [right]
and the VAMOS spectrometer [left] showed that the
balance between the two contributions was more
complex than previously envisaged.                                           

The complexity of the atomic nucleus reflects a multi-component character of the « nuclear force » that holds protons and neutrons together. Proper separation and characterization of each of these components represents a challenge for both theoretical and experimental nuclear structure studies. The tin isotopes (nuclei with Z=50 protons and a number of neutrons depending on the isotope) provide ideal opportunities to study the competition between two of the nuclear force components: the so-called pairing, related to the marked tendency of protons and neutrons to form pairs in the nuclear matter, and the so-called quadrupole interaction term, describing the natural susceptibility of nuclei to adopt deformed shapes. Though of a different nature, these two interaction terms contribute to the goal of achieving an optimum organization of nucleons in the atomic nucleus that will minimize its energy.  Previous works have demonstrated that a shift of balance between these two components takes place when approaching tin-100, and this observation provided important constraints for theoretical descriptions of this so-called “doubly-magic” nucleus. Having the same numbers of protons and neutrons (Z=N=50), 100Sn is a key nucleus to validate model descriptions of exotic nuclei.


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