Empirical signatures of shape phase transitions in nuclei with odd nucleon numbers

TL;DR

This paper proposes nuclear level density at low energies as a new indicator of first order phase transitions in nuclei, revealing different transition mechanisms across nuclear regions and identifying potential critical point nuclei in odd-mass and odd-odd systems.

Contribution

It introduces a novel signature based on level density maxima to detect phase transitions and applies it to odd-nucleon nuclei, enhancing understanding of nuclear shape phase behavior.

Findings

Level density maximum signals phase transition points.

Different transition mechanisms observed in N=90 and N=60 regions.

Candidates for critical point nuclei identified among odd-mass and odd-odd nuclei.

Abstract

Nuclear level density at low excitation energies is proposed as an indicator of the first order phase transitions in nuclei. The new signature, a maximum value of the level density at the critical point, appears to be sensitive to the detailed way the phase transition takes place in different nuclear regions: it is consistent with phase coexistence in the N=90 region, and with a rapid crossing of the two phases, without their coexistence/mixing at the critical point in the N=60 region, respectively. Candidates for critical point nuclei are proposed for odd-mass and odd-odd nuclei, using correlations between relative excitation energies, and their ratios, for structures (bands) based on unique-parity orbitals.