Publication

Lifetimes of Yrast States in 110Cd

Nuclear physics

Nuclear Physics A 565 (1993) 671

Authors:

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

Summary

The study measured the lifetimes of 20 yrast states in ¹¹⁰Cd (Z=48, N=62) using the recoil-distance method with the NORDBALL array of Compton-suppressed Ge detectors.

Key findings include:

  • Reduced Transition Probabilities: Enhanced B(E2) values for low-lying states (e.g., B(E2; 2⁺₁→0⁺₁) = 0.19 ± 0.02 e²b²) indicated quadrupole collectivity, consistent with vibrational excitations. However, higher-spin states (I ≥ 10ħ) exhibited reduced collectivity, suggesting a transition to single-particle or mixed-symmetry configurations.
  • Rotational-Vibrational Interplay: The data revealed coexisting rotational and vibrational behaviors. For instance, the 4⁺₁→2⁺₁ transition (B(E2) = 0.16 ± 0.02 e²b²) aligned with vibrational models, while backbending in the yrast sequence at ℏω ≈ 0.35 MeV signaled quasiparticle alignment and rotational effects.
  • Non-Collective States: Lifetime limits (<0.5 ps) for high-spin states (e.g., 12⁺₁) implied weak collectivity, attributed to proton g₉/₂ orbital excitations. These states contrasted sharply with collective low-spin levels, highlighting configuration-dependent structure changes.
  • Model Comparisons: The results were compared to Interacting Boson Model (IBM) and cranked shell model (CSM) predictions. While IBM-2 captured low-spin collectivity, CSM better described high-spin alignment effects, underscoring ¹¹⁰Cd’s transitional nature between spherical and deformed regimes.

The study provided critical empirical input for understanding shape coexistence and the interplay of collective vs. single-particle degrees of freedom near the N=62 subshell closure.

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