Enhanced photoneutron cross sections for zirconium isotopes near threshold: evidence for extra M1 strength?

Journal Article · Mon May 12 04:00:00 EDT 2008 · AIP Conference Proceedings

DOI:https://doi.org/10.1063/1.2939288· OSTI ID:21143341

Utsunomiya, H; Makinaga, A; Kaihori, T; Kondo, T; Yamagata, T; Akimune, H ^[1]; Goriely, S ^[2]; Koning, A J ^[3]; Hilaire, S ^[4]; Goko, S ^[5]; Toyokawa, H; Matsumoto, T; Harano, H ^[6]; Lui, Y -W ^[7]

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1. Department of Physics, Konan University, Okamoto 8-9-1, Higashinada, Kobe 658-8501 (Japan)
2. Institut d'Astronomie et d'Astrophysique, Universite Libre de Bruxelle, Campus de la Plane, CP-226, 1050 Brussels (Belgium)
3. Nuclear Research and Consultancy Group, P.O. Box 25, NL-1755 ZG Petten (Netherlands)
4. Departement de Physique Theorique et Appliquee, Service de Physique Nucleaire, B.P. 12--F-91680 Bruyeres-le-Chatel (France)
5. Japan Atomic Energy Agency, Tokai-mura, Naka, Ibaraki 319-1195 (Japan)
6. National Institute of Advanced Industrial Science and Technology, Tsukuba 305-8568 (Japan)
7. Cyclotron Institute, Texas A and M University, College Station, Texas 77843 (United States)

Photoneutron cross sections were measured for {sup 91}Zr, {sup 92}Zr and {sup 94}Zr near the neutron separation energy with quasi-monochromatic {gamma} rays. Some systematic extra strength is found around the neutron threshold and identified, through a coherent analysis of {sup 92}Zr({gamma},n){sup 91}Zr and {sup 91}Zr(n,{gamma}){sup 92}Zr cross sections, as being most probably a strong M1 resonance. The microscopic HFB+QRPA model for the E1 strength with the additional contribution of a strong M1 resonance at 9 MeV is found to explain all the reaction cross section data available. With such an M1 resonance strength tuned on the {sup 92}Zr({gamma},n){sup 91}Zr reaction, the photoneutron cross section of {sup 91}Zr and {sup 94}Zr are also found to be in good agreement with our new experimental data in the vicinity of the threshold and of the M1 peak energy. The present extra component in the photoneutron channel is qualitatively consistent with the M1 giant resonance reported in the inelastic proton scattering.

• OSTI ID: 21143341
• Journal Information: AIP Conference Proceedings, Journal Name: AIP Conference Proceedings Journal Issue: 1 Vol. 1012; ISSN APCPCS; ISSN 0094-243X
• Country of Publication: United States
• Language: English

Related Subjects

73 NUCLEAR PHYSICS AND RADIATION PHYSICS
CROSS SECTIONS
E1-TRANSITIONS
GIANT RESONANCE
HARTREE-FOCK-BOGOLYUBOV THEORY
INELASTIC SCATTERING
M1-TRANSITIONS
MEV RANGE
NEUTRON REACTIONS
NEUTRON SEPARATION ENERGY
PHOTONEUTRONS
PHOTONUCLEAR REACTIONS
PROTONS
RANDOM PHASE APPROXIMATION
STRENGTH FUNCTIONS
TUNNEL EFFECT
ZIRCONIUM 91
ZIRCONIUM 92
ZIRCONIUM 94