Transition from the Seniority to the Anharmonic Vibrator Regime in Nuclei

TL;DR

This paper investigates the transition from seniority to anharmonic vibrational regimes in nuclei using a shell model, highlighting the neutron-proton interaction's role in phase transitions between these collective behaviors.

Contribution

It introduces a shell model framework to qualitatively reproduce the transition between seniority and anharmonic vibrational regimes in nuclei.

Findings

Qualitative reproduction of transitional behavior in nuclei.

Confirmation of neutron-proton interaction's role in phase transition.

Identification of three classes of collective nuclei with sharp phase boundaries.

Abstract

A recent analysis of experimental energy systematics suggests that all collective nuclei fall into one of three classes -- seniority, anharmonic vibrational, or rotational -- with sharp phase transitions between them. We investigate the transition from the seniority to the anharmonic vibrator regime within a shell model framework involving a single large j-orbit. The calculations qualitatively reproduce the observed transitional behavior, both for U(5) like and O(6) like nuclei. They also confirm the preeminent role played by the neutron-proton interaction in producing the phase transition.