First observation of low-energy γ -ray enhancement in the rare-earth region

A. Simon; M. Guttormsen; A. C. Larsen; C. W. Beausang; P. Humby; J. T. Burke; R. J. Casperson; R. O. Hughes; T. J. Ross; J. M. Allmond; R. Chyzh; M. Dag; J. Koglin; E. McCleskey; M. McCleskey; S. Ota; A. Saastamoinen

doi:10.1103/PhysRevC.93.034303

First observation of low-energy γ -ray enhancement in the rare-earth region

A. Simon, M. Guttormsen, A. C. Larsen, C. W. Beausang, P. Humby, J. T. Burke, R. J. Casperson, R. O. Hughes, T. J. Ross, J. M. Allmond, R. Chyzh, M. Dag, J. Koglin, E. McCleskey, M. McCleskey, S. Ota, A. Saastamoinen

Nuclear Structure and Nuclear Astrophysi

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Abstract

The γ-ray strength function and level density in the quasi-continuum of Sm151,153 have been measured using bismuth germanate shielded Ge clover detectors of the STARLiTeR system. The Compton shields allow an extraction of the γ strength down to unprecedentedly low γ energies of ≈500 keV. For the first time an enhanced low-energy γ-ray strength has been observed in the rare-earth region. In addition, for the first time both the upbend and the well-known scissors resonance have been observed simultaneously for the same nucleus. Hauser-Feshbach calculations show that this strength enhancement at low γ energies could have an impact of 2-3 orders of magnitude on the (n,γ) reaction rates for r-process nucleosynthesis.

Original language	English
Article number	034303
Journal	Physical Review C
Volume	93
Issue number	3
DOIs	https://doi.org/10.1103/PhysRevC.93.034303
State	Published - Mar 4 2016

Funding

This work was supported by the US Department of Energy under Grants No. DE-NA0001801, No. DE-FG02-05ER41379, and No. DE-AC52-07NA27344; the Research Council of Norway (NFR); and the National Science Foundation under Grant No. PHY-1430152 (JINA-CEE). A.C.L. acknowledges financial support from the Research Council of Norway, Grant No. 205528, and funding from the ERC-STG-2014 under Grant Agreement No. 637686.

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10.1103/PhysRevC.93.034303

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Simon, A., Guttormsen, M., Larsen, A. C., Beausang, C. W., Humby, P., Burke, J. T., Casperson, R. J., Hughes, R. O., Ross, T. J., Allmond, J. M., Chyzh, R., Dag, M., Koglin, J., McCleskey, E., McCleskey, M., Ota, S., & Saastamoinen, A. (2016). First observation of low-energy γ -ray enhancement in the rare-earth region. Physical Review C, 93(3), Article 034303. https://doi.org/10.1103/PhysRevC.93.034303

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title = "First observation of low-energy γ -ray enhancement in the rare-earth region",

abstract = "The γ-ray strength function and level density in the quasi-continuum of Sm151,153 have been measured using bismuth germanate shielded Ge clover detectors of the STARLiTeR system. The Compton shields allow an extraction of the γ strength down to unprecedentedly low γ energies of ≈500 keV. For the first time an enhanced low-energy γ-ray strength has been observed in the rare-earth region. In addition, for the first time both the upbend and the well-known scissors resonance have been observed simultaneously for the same nucleus. Hauser-Feshbach calculations show that this strength enhancement at low γ energies could have an impact of 2-3 orders of magnitude on the (n,γ) reaction rates for r-process nucleosynthesis.",

author = "A. Simon and M. Guttormsen and Larsen, {A. C.} and Beausang, {C. W.} and P. Humby and Burke, {J. T.} and Casperson, {R. J.} and Hughes, {R. O.} and Ross, {T. J.} and Allmond, {J. M.} and R. Chyzh and M. Dag and J. Koglin and E. McCleskey and M. McCleskey and S. Ota and A. Saastamoinen",

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year = "2016",

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doi = "10.1103/PhysRevC.93.034303",

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Simon, A, Guttormsen, M, Larsen, AC, Beausang, CW, Humby, P, Burke, JT, Casperson, RJ, Hughes, RO, Ross, TJ, Allmond, JM, Chyzh, R, Dag, M, Koglin, J, McCleskey, E, McCleskey, M, Ota, S & Saastamoinen, A 2016, 'First observation of low-energy γ -ray enhancement in the rare-earth region', Physical Review C, vol. 93, no. 3, 034303. https://doi.org/10.1103/PhysRevC.93.034303

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AU - Simon, A.

AU - Guttormsen, M.

AU - Larsen, A. C.

AU - Beausang, C. W.

AU - Humby, P.

AU - Burke, J. T.

AU - Casperson, R. J.

AU - Hughes, R. O.

AU - Ross, T. J.

AU - Allmond, J. M.

AU - Chyzh, R.

AU - Dag, M.

AU - Koglin, J.

AU - McCleskey, E.

AU - McCleskey, M.

AU - Ota, S.

AU - Saastamoinen, A.

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AB - The γ-ray strength function and level density in the quasi-continuum of Sm151,153 have been measured using bismuth germanate shielded Ge clover detectors of the STARLiTeR system. The Compton shields allow an extraction of the γ strength down to unprecedentedly low γ energies of ≈500 keV. For the first time an enhanced low-energy γ-ray strength has been observed in the rare-earth region. In addition, for the first time both the upbend and the well-known scissors resonance have been observed simultaneously for the same nucleus. Hauser-Feshbach calculations show that this strength enhancement at low γ energies could have an impact of 2-3 orders of magnitude on the (n,γ) reaction rates for r-process nucleosynthesis.

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First observation of low-energy γ -ray enhancement in the rare-earth region

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