Deviations from the Porter-Thomas distribution due to nonstatistical 𝛾 decay below the  150Nd neutron separation threshold

O. Papst; J. Isaak; V. Werner; D. Savran; N. Pietralla; G. Battaglia; T. Beck; M. Beuschlein; S. W. Finch; U. Friman-Gayer; K. E. Ide; R. V. F. Janssens; M. D. Jones; J. Kleemann; B. Löher; M. Scheck; M. Spieker; W. Tornow; R. Zidarova; A. Zilges

doi:10.1103/n6zw-zhz2

Deviations from the Porter-Thomas distribution due to nonstatistical 𝛾 decay below the ¹⁵⁰Nd neutron separation threshold

O. Papst, J. Isaak, V. Werner, D. Savran, N. Pietralla, G. Battaglia, T. Beck, M. Beuschlein, S. W. Finch, U. Friman-Gayer, K. E. Ide, R. V. F. Janssens, M. D. Jones, J. Kleemann, B. Löher, M. Scheck, M. Spieker, W. Tornow, R. Zidarova, A. Zilges

Physics

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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 𝛾 decays from 1⁻ states of 0.490(16) is observed for the nuclide ¹⁵⁰Nd. Assuming 𝜒²-distributed partial transition widths, this average branching ratio is related to a degree of freedom of 𝜈=1.93⁢(12), rejecting the validity of the Porter-Thomas distribution, requiring 𝜈 =1. The observed deviation can be explained by nonstatistical effects in the 𝛾-decay behavior with contributions in the range of 9.4(10)% up to 94(10)%.

Original language	English
Article number	052501
Number of pages	8
Journal	Physical Review Letters
Volume	135
Issue number	5
DOIs	https://doi.org/10.1103/n6zw-zhz2
Publication status	Published - 30 Jul 2025

Funding

This work has been funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation)—Project-ID 279384907—SFB 1245, Project-ID 460150577—ZI 510/10-2, and Project-ID 499256822—GRK 2891 “Nuclear Photonics, ” by the State of Hesse under the grant “Nuclear Photonics” within the LOEWE program (LOEWE/2/11/519/03/04.001(0008)/62), by the BMBF under Grant No. 05P21RDEN9, and by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics, under Grants No. DE-SC0023010, No. DE-FG02-97ER41041 (UNC), and No. DE-FG02-97ER41033 (Duke-TUNL). M. Scheck acknowledges financial support by the UK-STFC (Grant No. ST/P005101/1).

Keywords

Porter-Thomas distribution
partial transition widths
nuclear resonance fluorescence
photon beams
particle separation thresholds

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Cite this

Papst, O., Isaak, J., Werner, V., Savran, D., Pietralla, N., Battaglia, G., Beck, T., Beuschlein, M., Finch, S. W., Friman-Gayer, U., Ide, K. E., Janssens, R. V. F., Jones, M. D., Kleemann, J., Löher, B., Scheck, M., Spieker, M., Tornow, W., Zidarova, R., & Zilges, A. (2025). Deviations from the Porter-Thomas distribution due to nonstatistical 𝛾 decay below the ¹⁵⁰Nd neutron separation threshold. Physical Review Letters, 135(5), Article 052501 . https://doi.org/10.1103/n6zw-zhz2

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title = "Deviations from the Porter-Thomas distribution due to nonstatistical 𝛾 decay below the 150Nd 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 𝛾 decays from 1− states of 0.490(16) is observed for the nuclide 150Nd. Assuming 𝜒2-distributed partial transition widths, this average branching ratio is related to a degree of freedom of 𝜈=1.93⁢(12), rejecting the validity of the Porter-Thomas distribution, requiring 𝜈 =1. The observed deviation can be explained by nonstatistical effects in the 𝛾-decay behavior with contributions in the range of 9.4(10)\% up to 94(10)\%. ",

keywords = "Porter-Thomas distribution, partial transition widths, nuclear resonance fluorescence, photon beams, particle separation thresholds",

author = "O. Papst and J. Isaak and V. Werner and D. Savran and N. Pietralla and G. Battaglia and T. Beck and M. Beuschlein and S. W. Finch and U. Friman-Gayer and K. E. Ide and R. V. F. Janssens and M. D. Jones and J. Kleemann and B. L{\"o}her and M. Scheck and M. Spieker and W. Tornow and R. Zidarova and A. Zilges",

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Papst, O, Isaak, J, Werner, V, Savran, D, Pietralla, N, Battaglia, G, Beck, T, Beuschlein, M, Finch, SW, Friman-Gayer, U, Ide, KE, Janssens, RVF, Jones, MD, Kleemann, J, Löher, B, Scheck, M, Spieker, M, Tornow, W, Zidarova, R & Zilges, A 2025, 'Deviations from the Porter-Thomas distribution due to nonstatistical 𝛾 decay below the ¹⁵⁰Nd neutron separation threshold', Physical Review Letters, vol. 135, no. 5, 052501 . https://doi.org/10.1103/n6zw-zhz2

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T1 - Deviations from the Porter-Thomas distribution due to nonstatistical 𝛾 decay below the 150Nd neutron separation threshold

AU - Papst, O.

AU - Isaak, J.

AU - Werner, V.

AU - Savran, D.

AU - Pietralla, N.

AU - Battaglia, G.

AU - Beck, T.

AU - Beuschlein, M.

AU - Finch, S. W.

AU - Friman-Gayer, U.

AU - Ide, K. E.

AU - Janssens, R. V. F.

AU - Jones, M. D.

AU - Kleemann, J.

AU - Löher, B.

AU - Scheck, M.

AU - Spieker, M.

AU - Tornow, W.

AU - Zidarova, R.

AU - Zilges, A.

PY - 2025/7/30

Y1 - 2025/7/30

N2 - 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 𝛾 decays from 1− states of 0.490(16) is observed for the nuclide 150Nd. Assuming 𝜒2-distributed partial transition widths, this average branching ratio is related to a degree of freedom of 𝜈=1.93⁢(12), rejecting the validity of the Porter-Thomas distribution, requiring 𝜈 =1. The observed deviation can be explained by nonstatistical effects in the 𝛾-decay behavior with contributions in the range of 9.4(10)% up to 94(10)%.

AB - 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 𝛾 decays from 1− states of 0.490(16) is observed for the nuclide 150Nd. Assuming 𝜒2-distributed partial transition widths, this average branching ratio is related to a degree of freedom of 𝜈=1.93⁢(12), rejecting the validity of the Porter-Thomas distribution, requiring 𝜈 =1. The observed deviation can be explained by nonstatistical effects in the 𝛾-decay behavior with contributions in the range of 9.4(10)% up to 94(10)%.

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KW - nuclear resonance fluorescence

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KW - particle separation thresholds

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