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Constraints on the dipole photon strength for the odd uranium isotopes

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Constraints on the dipole photon strength for the odd uranium isotopes. / n_TOF Collaboration.

In: Physical Review C, Vol. 105, No. 2, 024618, 24.02.2022.

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@article{aa0c51bb40714ff9acd1dad3fca541b5,
title = "Constraints on the dipole photon strength for the odd uranium isotopes",
abstract = "Background: The photon strength functions (PSFs) and nuclear level density (NLD) are key ingredients for calculation of the photon interaction with nuclei, in particular the reaction cross sections. These cross sections are important especially in nuclear astrophysics and in the development of advanced nuclear technologies. Purpose: The role of the scissors mode in the M1 PSF of (well-deformed) actinides was investigated by several experimental techniques. The analyses of different experiments result in significant differences, especially on the strength of the mode. The shape of the low-energy tail of the giant electric dipole resonance is uncertain as well. In particular, some works proposed a presence of the E1 pygmy resonance just above 7 MeV. Because of these inconsistencies additional information on PSFs in this region is of great interest. Methods: The ?-ray spectra from neutron-capture reactions on the U234, U236, and U238 nuclei have been measured with the total absorption calorimeter of the n_TOF facility at CERN. The background-corrected sum-energy and multi-step-cascade spectra were extracted for several isolated s-wave resonances up to about 140 eV. Results: The experimental spectra were compared to statistical model predictions coming from a large selection of models of photon strength functions and nuclear level density. No combination of PSF and NLD models from literature is able to globally describe our spectra. After extensive search we were able to find model combinations with modified generalized Lorentzian (MGLO) E1 PSF, which match the experimental spectra as well as the total radiative widths. Conclusions: The constant temperature energy dependence is favored for a NLD. The tail of giant electric dipole resonance is well described by the MGLO model of the E1 PSF with no hint of pygmy resonance. The M1 PSF must contain a very strong, relatively wide, and likely double-resonance scissors mode. The mode is responsible for about a half of the total radiative width of neutron resonances and significantly affects the radiative cross section. ",
author = "{n_TOF Collaboration} and J. Moreno-Soto and S. Valenta and E. Berthoumieux and A. Chebboubi and M. Diakaki and W. Dridi and E. Dupont and F. Gunsing and M. Krticka and O. Litaize and O. Serot and O. Aberle and V. Alcayne and S. Amaducci and J. Andrzejewski and L. Audouin and V. B{\'e}cares and V. Babiano-Suarez and M. Bacak and M. Barbagallo and Th Benedikt and S. Bennett and J. Billowes and D. Bosnar and A. Brown and M. Busso and M. Caama{\~n}o and L. Caballero-Ontanaya and F. Calvi{\~n}o and M. Calviani and D. Cano-Ott and A. Casanovas and F. Cerutti and E. Chiaveri and N. Colonna and G. Cort{\'e}s and Cort{\'e}s-Giraldo, {M. A.} and L. Cosentino and S. Cristallo and Damone, {L. A.} and Davies, {P. J.} and M. Dietz and C. Domingo-Pardo and R. Dressler and Q. Ducasse and I. Dur{\'a}n and Z. Eleme and B. Fern{\'a}ndez-Dom{\'i}nguez and A. Ferrari and T. Rauscher",
note = "Funding Information: The work was supported by the M{\v S}MT of the Czech Republic, the Charles University Project No. UNCE/SCI/013, and by the funding agencies of the participating institutes. Publisher Copyright: {\textcopyright} 2022 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.",
year = "2022",
month = feb,
day = "24",
doi = "10.1103/PhysRevC.105.024618",
language = "English",
volume = "105",
journal = "Physical Review C",
issn = "2469-9985",
publisher = "American Physical Society",
number = "2",

}

RIS

TY - JOUR

T1 - Constraints on the dipole photon strength for the odd uranium isotopes

AU - n_TOF Collaboration

AU - Moreno-Soto, J.

AU - Valenta, S.

AU - Berthoumieux, E.

AU - Chebboubi, A.

AU - Diakaki, M.

AU - Dridi, W.

AU - Dupont, E.

AU - Gunsing, F.

AU - Krticka, M.

AU - Litaize, O.

AU - Serot, O.

AU - Aberle, O.

AU - Alcayne, V.

AU - Amaducci, S.

AU - Andrzejewski, J.

AU - Audouin, L.

AU - Bécares, V.

AU - Babiano-Suarez, V.

AU - Bacak, M.

AU - Barbagallo, M.

AU - Benedikt, Th

AU - Bennett, S.

AU - Billowes, J.

AU - Bosnar, D.

AU - Brown, A.

AU - Busso, M.

AU - Caamaño, M.

AU - Caballero-Ontanaya, L.

AU - Calviño, F.

AU - Calviani, M.

AU - Cano-Ott, D.

AU - Casanovas, A.

AU - Cerutti, F.

AU - Chiaveri, E.

AU - Colonna, N.

AU - Cortés, G.

AU - Cortés-Giraldo, M. A.

AU - Cosentino, L.

AU - Cristallo, S.

AU - Damone, L. A.

AU - Davies, P. J.

AU - Dietz, M.

AU - Domingo-Pardo, C.

AU - Dressler, R.

AU - Ducasse, Q.

AU - Durán, I.

AU - Eleme, Z.

AU - Fernández-Domínguez, B.

AU - Ferrari, A.

AU - Rauscher, T.

N1 - Funding Information: The work was supported by the MŠMT of the Czech Republic, the Charles University Project No. UNCE/SCI/013, and by the funding agencies of the participating institutes. Publisher Copyright: © 2022 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

PY - 2022/2/24

Y1 - 2022/2/24

N2 - Background: The photon strength functions (PSFs) and nuclear level density (NLD) are key ingredients for calculation of the photon interaction with nuclei, in particular the reaction cross sections. These cross sections are important especially in nuclear astrophysics and in the development of advanced nuclear technologies. Purpose: The role of the scissors mode in the M1 PSF of (well-deformed) actinides was investigated by several experimental techniques. The analyses of different experiments result in significant differences, especially on the strength of the mode. The shape of the low-energy tail of the giant electric dipole resonance is uncertain as well. In particular, some works proposed a presence of the E1 pygmy resonance just above 7 MeV. Because of these inconsistencies additional information on PSFs in this region is of great interest. Methods: The ?-ray spectra from neutron-capture reactions on the U234, U236, and U238 nuclei have been measured with the total absorption calorimeter of the n_TOF facility at CERN. The background-corrected sum-energy and multi-step-cascade spectra were extracted for several isolated s-wave resonances up to about 140 eV. Results: The experimental spectra were compared to statistical model predictions coming from a large selection of models of photon strength functions and nuclear level density. No combination of PSF and NLD models from literature is able to globally describe our spectra. After extensive search we were able to find model combinations with modified generalized Lorentzian (MGLO) E1 PSF, which match the experimental spectra as well as the total radiative widths. Conclusions: The constant temperature energy dependence is favored for a NLD. The tail of giant electric dipole resonance is well described by the MGLO model of the E1 PSF with no hint of pygmy resonance. The M1 PSF must contain a very strong, relatively wide, and likely double-resonance scissors mode. The mode is responsible for about a half of the total radiative width of neutron resonances and significantly affects the radiative cross section.

AB - Background: The photon strength functions (PSFs) and nuclear level density (NLD) are key ingredients for calculation of the photon interaction with nuclei, in particular the reaction cross sections. These cross sections are important especially in nuclear astrophysics and in the development of advanced nuclear technologies. Purpose: The role of the scissors mode in the M1 PSF of (well-deformed) actinides was investigated by several experimental techniques. The analyses of different experiments result in significant differences, especially on the strength of the mode. The shape of the low-energy tail of the giant electric dipole resonance is uncertain as well. In particular, some works proposed a presence of the E1 pygmy resonance just above 7 MeV. Because of these inconsistencies additional information on PSFs in this region is of great interest. Methods: The ?-ray spectra from neutron-capture reactions on the U234, U236, and U238 nuclei have been measured with the total absorption calorimeter of the n_TOF facility at CERN. The background-corrected sum-energy and multi-step-cascade spectra were extracted for several isolated s-wave resonances up to about 140 eV. Results: The experimental spectra were compared to statistical model predictions coming from a large selection of models of photon strength functions and nuclear level density. No combination of PSF and NLD models from literature is able to globally describe our spectra. After extensive search we were able to find model combinations with modified generalized Lorentzian (MGLO) E1 PSF, which match the experimental spectra as well as the total radiative widths. Conclusions: The constant temperature energy dependence is favored for a NLD. The tail of giant electric dipole resonance is well described by the MGLO model of the E1 PSF with no hint of pygmy resonance. The M1 PSF must contain a very strong, relatively wide, and likely double-resonance scissors mode. The mode is responsible for about a half of the total radiative width of neutron resonances and significantly affects the radiative cross section.

UR - http://www.scopus.com/inward/record.url?scp=85126030323&partnerID=8YFLogxK

U2 - 10.1103/PhysRevC.105.024618

DO - 10.1103/PhysRevC.105.024618

M3 - Article

AN - SCOPUS:85126030323

VL - 105

JO - Physical Review C

JF - Physical Review C

SN - 2469-9985

IS - 2

M1 - 024618

ER -