Publication

High-Spin States in 109, 111Cd and 107Pd

Nuclear physics

Nuclear Physics A 577 (1994) 727.

Authors:

S. Juutinen, P. Simecek, C. Fahlander, R. Julin, J. Kumpulainen, A. Lampinen, T. Lönnroth, A. Maj, S. Mitarai, D. Müller, J. Nyberg, M. Piiparinen, M. Sugawara, I. Thorslund, S. Törmänen, A. Virtanen

Summary

The study investigates the nuclear structure of neutron-rich cadmium and palladium isotopes using heavy-ion fusion-evaporation reactions and γ-ray spectroscopy.

Key findings include:

  • Rotational Band Identification: High-spin states in ¹⁰⁹,¹¹¹Cd and ¹⁰⁷Pd were populated via reactions such as ¹⁰⁶Cd(⁷Li, 4nγ)¹⁰⁹Cd and ¹¹⁰Cd(α, 3nγ)¹¹¹Cd, revealing new deformed rotational bands with backbends attributed to the alignment of h₁₁/₂ quasineutrons. These bands exhibit prolate deformation with β₂ ≈ 0.2118.
  • Comparison with Models: The observed band properties—including moment-of-inertia changes and transition energies—align with predictions from the cranked shell model (CSM) and total Routhian surface (TRS) calculations, confirming the role of neutron alignment in driving shape changes at high spins.
  • Deformation Insights: The study highlights moderate quadrupole deformation in these nuclei, contrasting with near-spherical configurations at lower spins. Enhanced E2 transition strengths and signature splitting in rotational bands underscore residual collectivity near the N=60 neutron shell closure.
  • Methodology: Experimental results from γ-γ coincidence measurements and angular correlation analyses extended the level schemes, identifying new isomers and transitions. For instance, ¹⁰⁷Pd exhibited a rotational cascade up to spin I ≈ 25/2, with backbending near ℏω ≈ 0.4 MeV.

This work provides critical empirical data for understanding collective behavior and single-particle effects in neutron-rich nuclei, bridging gaps between shell-model and collective-model descriptions.

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