Deviations from the Porter-Thomas Distribution due to Nonstatistical $\gamma$ Decay below the ${}^{150}$Nd Neutron Separation Threshold

Abstract

We introduce a new method for the study of fluctuations of partial transition widths based on nuclear resonance fluorescence experiments with quasimonochromatic linearly polarized photon beams below particle separation thresholds. It is based on the average branching of decays of $J=1$ states of an even-even nucleus to the $2_1^{+}$ state in comparison to the ground state. Between 5 and 7 MeV, a constant average branching ratio for $\gamma$ decays from $1^{-}$ states of 0.490(16) is observed for the nuclide ${}^{150}$Nd. Assuming ${\chi }^2$-distributed partial transition widths, this average branching ratio is related to a degree of freedom of $\nu =1.93(12)$, rejecting the validity of the Porter-Thomas distribution, requiring $\nu =1$. The observed deviation can be explained by nonstatistical effects in the $\gamma$-decay behavior with contributions in the range of 9.4(10)% up to 94(10)%.

arXiv comment7 pages, 2 figures

References in corpus (25)

• MCMC using Hamiltonian dynamics
• Random Matrix Theories in Quantum Physics: Common Concepts
• Characterizing Quantum Supremacy in Near-Term Devices
• Random Matrices and Chaos in Nuclear Physics
• Quantum Supremacy and the Complexity of Random Circuit Sampling
• Random Matrices and Chaos in Nuclear Physics: Nuclear Reactions
• Reference Database for Photon Strength Functions
• Statistical Hauser-Feshbach theory with width fluctuation correction including direct reaction channels for neutron induced reaction at low energies
• Anomalous fluctuations of s-wave reduced neutron widths of ${}^{192,194}$Pt resonances
• The high-efficiency γ-ray spectroscopy setup γ3 at HIγS
• Distribution of Resonance Widths and Dynamics of Continuum Coupling
• Independent Normalization for $\gamma$-ray Strength Functions: The Shape Method
• Resonance analysis of ${}^{147}$Sm(n,alpha) cross sections: Comparison to optical model calculations and indications of non-statistical effects
• Distribution of Partial Neutron Widths for Nuclei close to a Maximum of the Neutron Strength Function
• Parity assignments in 172,174Yb using polarized photons and the K quantum number in rare earth nuclei
• Reduced neutron widths in the nuclear data ensemble: Experiment and theory do not agree
• Spin measurements for 147Sm+n resonances: Further evidence for non-statistical effects
• Modification of the Porter-Thomas distribution by rank-one interaction
• Gamma decay of the ${}^{154}$Sm Isovector Giant Dipole Resonance: Smekal-Raman Scattering as a Novel Probe of Nuclear Ground-State Deformation
• Neutron Resonance Widths and the Porter-Thomas Distribution
• Strong enhancement of level densities in the crossover from spherical to deformed neodymium isotopes
• TENDL-astro: a new nuclear data set for astrophysics interest
• Random-matrix models of monitored quantum circuits
• Fock-space delocalization and the emergence of the Porter-Thomas distribution from dual-unitary dynamics
• Abrupt Change in Radiation-Width Distribution for 147Sm Neutron Resonances