Publication

The Role of the Shape Driving h11/2 Neutron Orbital in 108Cd

Nuclear physics

Nuclear Physics A 564 (1993) 285

Authors:

I. Thorslund, C. Fahlander, J. Nyberg, S. Juutinen, R. Julin, M. Piiparinen, R. Wyss, A. Lampinen, T. Lönnroth, D. Müller, S. Törmanen, A. Virtanen

Summary

The publication investigates the interplay between nuclear deformation and neutron alignment using γ-ray spectroscopy following heavy-ion fusion-evaporation reactions.

Key findings include:

  • Neutron Alignment: The alignment of h₁₁/₂ neutrons drives a transition from vibrational to rotational structures at high spins. A backbend in the yrast sequence at ℏω ≈ 0.35 MeV signals quasiparticle alignment, stabilizing prolate deformation (β₂ ≈ 0.2) in ¹⁰⁸Cd.
  • Shape Evolution: Below the backbend (I < 10ħ), the nucleus exhibits vibrational collectivity with enhanced B(E2) values (~40 W.u.), while higher-spin states (I ≥ 10ħ) transition to rotational behavior dominated by aligned h₁₁/₂ and g₇/₂ neutrons.
  • Model Comparisons: The data align with cranked shell model (CSM) predictions for rotational alignment but reveal discrepancies in moment-of-inertia trends, highlighting contributions from core-polarization effects and valence neutron-proton interactions.
  • Anti-Magnetic Rotation: The 16⁺ state, identified as the bandhead of an anti-magnetic rotational band, features a π(g₉/₂)⁻² ⊗ ν(h₁₁/₂)²(g₇/₂)² configuration, supported by measured g-factors (−0.09) and reduced collectivity.

The study underscores the h₁₁/₂ neutron orbital as critical for driving shape transitions and collective behavior in near-magic nuclei like ¹⁰⁸Cd, bridging vibrational and rotational models.

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