The magic nature of 132Sn explored through the single-particle states of 133Sn

TL;DR

This study investigates the single-particle states of 133Sn outside the doubly magic nucleus 132Sn, confirming its magic nature and providing insights into nuclear structure relevant for nucleosynthesis.

Contribution

The paper provides the first detailed measurement of single-particle states outside 132Sn, demonstrating the purity of these states and reinforcing the magic nature of 132Sn.

Findings

Single-particle states in 133Sn are well-defined and pure.

The results confirm the magic nature of 132Sn.

Insights into nuclear structure relevant for the r-process nucleosynthesis.

Abstract

Atomic nuclei have a shell structure where nuclei with 'magic numbers' of neutrons and protons are analogous to the noble gases in atomic physics. Only ten nuclei with the standard magic numbers of both neutrons and protons have so far been observed. The nuclear shell model is founded on the precept that neutrons and protons can move as independent particles in orbitals with discrete quantum numbers, subject to a mean field generated by all the other nucleons. Knowledge of the properties of single-particle states outside nuclear shell closures in exotic nuclei is important for a fundamental understanding of nuclear structure and nucleosynthesis (for example the r-process, which is responsible for the production of about half of the heavy elements). However, as a result of their short lifetimes, there is a paucity of knowledge about the nature of single-particle states outside exotic doubly magic nuclei. Here we measure the single-particle character of the levels in 133Sn that lie outside the double shell closure present at the short-lived nucleus 132Sn. We use an inverse kinematics technique that involves the transfer of a single nucleon to the nucleus. The purity of the measured single-particle states clearly illustrates the magic nature of 132Sn.