Novel Shape Evolution in Sn Isotopes from Magic Numbers 50 to 82

Area of Science:

• Nuclear Physics
• Atomic Physics
• Quantum Mechanics

Background:

• The behavior of tin (Sn) isotopes has been a long-standing puzzle in nuclear physics.
• Understanding shape evolution and phase transitions in atomic nuclei is crucial for nuclear structure theory.

Purpose of the Study:

• To present a unified explanation for the novel shape evolution observed in Sn isotopes (100-138Sn).
• To elucidate the underlying mechanisms driving the significant increase in B(E2;0_{1}^{+}→2_{1}^{+}) values around 110Sn.
• To identify and characterize quantum phase transitions in this isotopic chain.

Main Methods:

• State-of-the-art Monte Carlo shell model calculations.
• Utilizing a large model space with eight single-particle orbits for protons and neutrons.
• Activating protons in the 1g_{9/2} orbital with a fixed Hamiltonian and effective charges.

Main Results:

• A novel shape evolution across the Sn isotopes (100-138Sn) is successfully explained.
• The increase in B(E2;0_{1}^{+}→2_{1}^{+}) values is attributed to shape evolution driven by proton excitations from the 1g_{9/2} orbital.
• A second-order quantum phase transition is identified around neutron number N=66, linking deformed and spherical pairing phases.

Conclusions:

• The study provides a comprehensive description of shape and shell evolution in Sn isotopes.
• Findings cover phenomena from the Gamow-Teller decay of 100Sn to the enhanced double magicity of 132Sn.
• Proton excitations play a key role in the observed nuclear structure changes.