178
J. L. Ullmann et al.
to calculate the shape of gamma-ray spectra observed in 234,236,238 U(n, γ ) and
239 Pu(n, γ ) reactions, and that additional strength at low energies (2 to 3 MeV),
most likely an M1 scissors-mode resonance, is required. Accurate calculations of
the capture cross section can be made by including the scissors mode in the photon
strength function, with proper choice of models for the level density and E1 portion
of the strength function. We note that the calculations are sensitive to the input
parameters, and precise data and theory are needed to fix the models and their
parameters.
References
1. M.R. Mumpower et al., Estimation of M1 scissors mode strength for deformed nuclei in the
medium to heavy mass region by statistical Hauser-Feshbach model calculations. Phys. Rev. C
96, 024612 (2017)
2. S. Hilaire, S. Goriely, Towards more predictive nuclear reaction modelling, in Proceedings of
the 6th International Workshop on Compound-Nuclear Reactions and Related Topics (Springer
International Publishing, Cham, 2021)
3. F. Beˇ cvᡠr, Simulation of γ cascades in complex nuclei with emphasis on assessment of
uncertainties of cascade-related quantities. Nucl. Instr. Meth. A 417, 434 (1998)
4. M. Jandel et al., GEANT4 simulations of the DANCE array. Nucl. Instru. Meth. B 261, 1117
(2007)
5. T. Kawano, P. Talou, M.B. Chadwick, T. Watanabe, Monte Carlo simulation for particle and
γ -ray emissions in statistical Hauser-Feshbach model. J. Nucl. Sci. Technol. 47, 462 (2010)
6. J. Kopecky, M. Uhl, Test of gamma-ray strength functions in nuclear reaction model calculations. Phys. Rev. C 41, 1941 (1990)
7. M. Herman et al., EMPIRE-3.2 Malta (rev.1) Modular system for nuclear data calculations and
nuclear data evaluation User’s Manual, INDC(NDS)-0603, 2015. Nucl. Data Sheets 108, 2655
(2007). www-nds.iaea.org/empire/resources/empire.pdf
8. M. Guttormsen et al., Scissors resonance in the quasicontinuum of Th, Pa, and U isotopes.
Phys. Rev. C 89, 014302 (2014)
9. J.L. Ullmann et al., Cross section and γ -ray spectra for 238 U(n, γ ) measured with the DANCE
detector array at the Los Alamos Neutron Science Center. Phys. Rev. C 89, 034603 (2014)
10. J.L. Ullmann et al., Constraining the calculation of 234,236,238 U(n,γ ) cross sections with
measurements of the gamma-ray spectra at DANCE. Phys. Rev. C 96, 024627 (2017)
11. J. Kroll et al., Strength of the scissors mode in odd-mass Gd isotopes from the radiative capture
of resonance neutrons. Phys. Rev. C 88, 034317 (2013)
12. S.S. Dietrich, B.L. Berman, Atlas of photoneutron cross sections obtained with monoenergetic
photons. At. Data Nucl. Data Tables 38, 199 (1988)
13. T. Kawano, S. Chiba, H. Koura, Phenomenological nuclear level densities using the KTUY05
nuclear mass formula for applications off-stability. J. Nucl. Sci. Technol. 43, 1 (2006)
14. B. Baramsai et al., Radiative neutron Capture cross section from 236 U. Phs. Rev. C 96, 024619
(2017)
15. C.-Y. Wu et al., A compact gas-filled avalanche counter for DANCE. Nucl. Instrum. Meth. A
78, 694 (2012)
16. S. Mosby et al., Unifying measurement of 239 P u(n, γ ) in the keV to MeV energy regime.
Phys. Rev. C 97, 04160R (2018)
J. L. Ullmann et al.
to calculate the shape of gamma-ray spectra observed in 234,236,238 U(n, γ ) and
239 Pu(n, γ ) reactions, and that additional strength at low energies (2 to 3 MeV),
most likely an M1 scissors-mode resonance, is required. Accurate calculations of
the capture cross section can be made by including the scissors mode in the photon
strength function, with proper choice of models for the level density and E1 portion
of the strength function. We note that the calculations are sensitive to the input
parameters, and precise data and theory are needed to fix the models and their
parameters.
References
1. M.R. Mumpower et al., Estimation of M1 scissors mode strength for deformed nuclei in the
medium to heavy mass region by statistical Hauser-Feshbach model calculations. Phys. Rev. C
96, 024612 (2017)
2. S. Hilaire, S. Goriely, Towards more predictive nuclear reaction modelling, in Proceedings of
the 6th International Workshop on Compound-Nuclear Reactions and Related Topics (Springer
International Publishing, Cham, 2021)
3. F. Beˇ cvᡠr, Simulation of γ cascades in complex nuclei with emphasis on assessment of
uncertainties of cascade-related quantities. Nucl. Instr. Meth. A 417, 434 (1998)
4. M. Jandel et al., GEANT4 simulations of the DANCE array. Nucl. Instru. Meth. B 261, 1117
(2007)
5. T. Kawano, P. Talou, M.B. Chadwick, T. Watanabe, Monte Carlo simulation for particle and
γ -ray emissions in statistical Hauser-Feshbach model. J. Nucl. Sci. Technol. 47, 462 (2010)
6. J. Kopecky, M. Uhl, Test of gamma-ray strength functions in nuclear reaction model calculations. Phys. Rev. C 41, 1941 (1990)
7. M. Herman et al., EMPIRE-3.2 Malta (rev.1) Modular system for nuclear data calculations and
nuclear data evaluation User’s Manual, INDC(NDS)-0603, 2015. Nucl. Data Sheets 108, 2655
(2007). www-nds.iaea.org/empire/resources/empire.pdf
8. M. Guttormsen et al., Scissors resonance in the quasicontinuum of Th, Pa, and U isotopes.
Phys. Rev. C 89, 014302 (2014)
9. J.L. Ullmann et al., Cross section and γ -ray spectra for 238 U(n, γ ) measured with the DANCE
detector array at the Los Alamos Neutron Science Center. Phys. Rev. C 89, 034603 (2014)
10. J.L. Ullmann et al., Constraining the calculation of 234,236,238 U(n,γ ) cross sections with
measurements of the gamma-ray spectra at DANCE. Phys. Rev. C 96, 024627 (2017)
11. J. Kroll et al., Strength of the scissors mode in odd-mass Gd isotopes from the radiative capture
of resonance neutrons. Phys. Rev. C 88, 034317 (2013)
12. S.S. Dietrich, B.L. Berman, Atlas of photoneutron cross sections obtained with monoenergetic
photons. At. Data Nucl. Data Tables 38, 199 (1988)
13. T. Kawano, S. Chiba, H. Koura, Phenomenological nuclear level densities using the KTUY05
nuclear mass formula for applications off-stability. J. Nucl. Sci. Technol. 43, 1 (2006)
14. B. Baramsai et al., Radiative neutron Capture cross section from 236 U. Phs. Rev. C 96, 024619
(2017)
15. C.-Y. Wu et al., A compact gas-filled avalanche counter for DANCE. Nucl. Instrum. Meth. A
78, 694 (2012)
16. S. Mosby et al., Unifying measurement of 239 P u(n, γ ) in the keV to MeV energy regime.
Phys. Rev. C 97, 04160R (2018)