title: Enhanced γ-Ray Emission from Neutron Unbound States Populated in β Decay.
abstract: Total absorption spectroscopy is used to investigate the β-decay intensity to states above the neutron separation energy followed by γ-ray emission in (87,88)Br and (94)Rb. Accurate results are obtained thanks to a careful control of systematic errors. An unexpectedly large γ intensity is observed in all three cases extending well beyond the excitation energy region where neutron penetration is hindered by low neutron energy. The γ branching as a function of excitation energy is compared to Hauser-Feshbach model calculations. For (87)Br and (88)Br the γ branching reaches 57% and 20%, respectively, and could be explained as a nuclear structure effect. Some of the states populated in the daughter can only decay through the emission of a large orbital angular momentum neutron with a strongly reduced barrier penetrability. In the case of neutron-rich (94)Rb the observed 4.5% branching is much larger than the calculations performed with standard nuclear statistical model parameters, even after proper correction for fluctuation effects on individual transition widths. The difference can be reconciled by introducing an enhancement of 1 order of magnitude in the photon strength to neutron strength ratio. An increase in the photon strength function of such magnitude for very neutron-rich nuclei, if it proves to be correct, leads to a similar increase in the (n,γ) cross section that would have an impact on r process abundance calculations.
authors: Instituto de Fisica Corpuscular (CSIC-Universitat de Valencia), Apdo. Correos 22085, E-46071 Valencia, Spain.
authors: J L
authors: JL
authors: Tain
authors: Instituto de Fisica Corpuscular (CSIC-Universitat de Valencia), Apdo. Correos 22085, E-46071 Valencia, Spain.
authors: E
authors: E
authors: Valencia
authors: Instituto de Fisica Corpuscular (CSIC-Universitat de Valencia), Apdo. Correos 22085, E-46071 Valencia, Spain.
authors: A
authors: A
authors: Algora
authors: Instituto de Fisica Corpuscular (CSIC-Universitat de Valencia), Apdo. Correos 22085, E-46071 Valencia, Spain.
authors: J
authors: J
authors: Agramunt
authors: Instituto de Fisica Corpuscular (CSIC-Universitat de Valencia), Apdo. Correos 22085, E-46071 Valencia, Spain.
authors: B
authors: B
authors: Rubio
authors: University of Surrey, Department of Physics, Guildford GU2 7XH, United Kingdom.
authors: S
authors: S
authors: Rice
authors: University of Surrey, Department of Physics, Guildford GU2 7XH, United Kingdom.
authors: W
authors: W
authors: Gelletly
authors: University of Surrey, Department of Physics, Guildford GU2 7XH, United Kingdom.
authors: P
authors: P
authors: Regan
authors: SUBATECH, CNRS/IN2P3, Université de Nantes, Ecole des Mines, F-44307 Nantes, France.
authors: A-A
authors: AA
authors: Zakari-Issoufou
authors: SUBATECH, CNRS/IN2P3, Université de Nantes, Ecole des Mines, F-44307 Nantes, France.
authors: M
authors: M
authors: Fallot
authors: SUBATECH, CNRS/IN2P3, Université de Nantes, Ecole des Mines, F-44307 Nantes, France.
authors: A
authors: A
authors: Porta
authors: University of Jyväskylä, Department of Physics, P.O. Box 35, FI-40014 Jyväskylä, Finland.
authors: J
authors: J
authors: Rissanen
authors: University of Jyväskylä, Department of Physics, P.O. Box 35, FI-40014 Jyväskylä, Finland.
authors: T
authors: T
authors: Eronen
authors: Helsinki Institute of Physics, University of Helsinki, FI00014 Helsinki, Finland.
authors: J
authors: J
authors: Äystö
authors: Petersburg Nuclear Physics Institute, RU-188300 Gatchina, Russia.
authors: L
authors: L
authors: Batist
authors: University of Surrey, Department of Physics, Guildford GU2 7XH, United Kingdom.
authors: M
authors: M
authors: Bowry
authors: SUBATECH, CNRS/IN2P3, Université de Nantes, Ecole des Mines, F-44307 Nantes, France.
authors: V M
authors: VM
authors: Bui
authors: Universitat Politecnica de Catalunya, E-08028 Barcelona, Spain.
authors: R
authors: R
authors: Caballero-Folch
authors: Centro de Investigaciones Energéticas Medioambientales y Tecnólogicas, E-28040 Madrid, Spain.
authors: D
authors: D
authors: Cano-Ott
authors: University of Jyväskylä, Department of Physics, P.O. Box 35, FI-40014 Jyväskylä, Finland.
authors: V-V
authors: VV
authors: Elomaa
authors: Instituto de Fisica Corpuscular (CSIC-Universitat de Valencia), Apdo. Correos 22085, E-46071 Valencia, Spain.
authors: E
authors: E
authors: Estevez
authors: University of Surrey, Department of Physics, Guildford GU2 7XH, United Kingdom.
authors: G F
authors: GF
authors: Farrelly
authors: Centro de Investigaciones Energéticas Medioambientales y Tecnólogicas, E-28040 Madrid, Spain.
authors: A R
authors: AR
authors: Garcia
authors: Universitat Politecnica de Catalunya, E-08028 Barcelona, Spain.
authors: B
authors: B
authors: Gomez-Hornillos
authors: Universitat Politecnica de Catalunya, E-08028 Barcelona, Spain.
authors: V
authors: V
authors: Gorlychev
authors: University of Jyväskylä, Department of Physics, P.O. Box 35, FI-40014 Jyväskylä, Finland.
authors: J
authors: J
authors: Hakala
authors: Instituto de Fisica Corpuscular (CSIC-Universitat de Valencia), Apdo. Correos 22085, E-46071 Valencia, Spain.
authors: M D
authors: MD
authors: Jordan
authors: University of Jyväskylä, Department of Physics, P.O. Box 35, FI-40014 Jyväskylä, Finland.
authors: A
authors: A
authors: Jokinen
authors: University of Jyväskylä, Department of Physics, P.O. Box 35, FI-40014 Jyväskylä, Finland.
authors: V S
authors: VS
authors: Kolhinen
authors: Nuclear Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439, USA.
authors: F G
authors: FG
authors: Kondev
authors: Centro de Investigaciones Energéticas Medioambientales y Tecnólogicas, E-28040 Madrid, Spain.
authors: T
authors: T
authors: Martínez
authors: Centro de Investigaciones Energéticas Medioambientales y Tecnólogicas, E-28040 Madrid, Spain.
authors: E
authors: E
authors: Mendoza
authors: University of Jyväskylä, Department of Physics, P.O. Box 35, FI-40014 Jyväskylä, Finland.
authors: I
authors: I
authors: Moore
authors: University of Jyväskylä, Department of Physics, P.O. Box 35, FI-40014 Jyväskylä, Finland.
authors: H
authors: H
authors: Penttilä
authors: University of Surrey, Department of Physics, Guildford GU2 7XH, United Kingdom.
authors: Zs
authors: Z
authors: Podolyák
authors: University of Jyväskylä, Department of Physics, P.O. Box 35, FI-40014 Jyväskylä, Finland.
authors: M
authors: M
authors: Reponen
authors: University of Jyväskylä, Department of Physics, P.O. Box 35, FI-40014 Jyväskylä, Finland.
authors: V
authors: V
authors: Sonnenschein
authors: NNDC, Brookhaven National Laboratory, Upton, New York 11973, USA.
authors: A A
authors: AA
authors: Sonzogni