Giant dipole resonance in sup 17 O observed with the (. gamma. , p ) reaction

Journal Article · Wed Jan 01 00:00:00 EST 1992 · Physical Review, C (Nuclear Physics); (United States)

DOI:https://doi.org/10.1103/PhysRevC.45.174· OSTI ID:5081825

Zubanov, D; Thompson, M N ^[1]; Berman, B L ^[2]; Jury, J W ^[3]; Pywell, R E ^[4]; McNeill, K G ^[5]

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1. School of Physics, University of Melbourne, Parkville, Victoria 3052 (Australia)
2. Center for Nuclear Studies, Department of Physics, The George Washington University, Washington, D.C. 20052 (United States)
3. Department of Physics, Trent University, Peterborough, Ontario, K9J 7B8 (Canada)
4. Accelerator Laboratory, University of Saskatchewan, Saskatoon, Saskatchewan, S7N 0W0 (Canada)
5. Department of Physics, University of Toronto, Toronto, Ontario, M5S 1A7 (Canada)

The giant dipole resonance (GDR) in {sup 17}O has been studied with the reaction {sup 17}O({gamma},{ital p}){sup 16}N from {ital E}{sub {gamma}}=13.50 to 43.15 MeV using quasimonoenergetic photons. The measured cross section shows major peaks at 15.1, 18.1, 19.3, 20.3, 22.2, 23.1, 24.4, and {similar to}26.5 MeV. The intermediate structure in the main GDR region is remarkably similar to that observed in {sup 16}O, indicating that the valence neutron outside the doubly magic {sup 16}O core perturbs the core-excited states minimally, in support of the weak-coupling hypothesis. We correlate the trends in GDR structure of {sup 16,17,18}O with changes in ground-state properties related to static deformation. The ({gamma},{ital p}) reaction selects strength predominantly from two-particle--one-hole configurations formed via {ital E}1 transitions from the 1{ital p}{sub 1/2} subshell; comparison with other reactions (photoneutron and radiative capture) provides information on the microscopic structure of {ital E}1 states. The peak observed near threshold at 15.1 MeV is remarkably strong; we infer that it originates from photoexcitation of a few narrow {ital T}=3/2 states and that {ital M}1 transitions contribute to the measured strength. The total absorption cross section is approximated by summing the ({gamma},{ital p}) cross section and the previously published photoneutron cross section; comparison with particle-hole shell-model calculations shows that the main cross-section features, including isospin distribution, are well predicted. Evidence is found for isospin splitting in {sup 17}O. Systematics of the integrated cross sections for the carbon, nitrogen, and oxygen isotopes are delineated.

• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 5081825
• Journal Information: Physical Review, C (Nuclear Physics); (United States), Vol. 45:1; ISSN 0556-2813
• Country of Publication: United States
• Language: English

Related Subjects

73 NUCLEAR PHYSICS AND RADIATION PHYSICS
OXYGEN 17
PHOTOPROTONS
DIFFERENTIAL CROSS SECTIONS
E1-TRANSITIONS
GIANT RESONANCE
ISOSPIN
MEV RANGE 10-100
PHOTONUCLEAR REACTIONS
SHELL MODELS
BARYONS
CROSS SECTIONS
ELEMENTARY PARTICLES
ENERGY RANGE
ENERGY-LEVEL TRANSITIONS
EVEN-ODD NUCLEI
FERMIONS
HADRONS
ISOTOPES
LIGHT NUCLEI
MATHEMATICAL MODELS
MEV RANGE
MULTIPOLE TRANSITIONS
NUCLEAR MODELS
NUCLEAR REACTIONS
NUCLEI
NUCLEONS
OXYGEN ISOTOPES
PARTICLE PROPERTIES
PROTONS
RESONANCE
STABLE ISOTOPES
663450* - Heavy-Ion-Induced Reactions & Scattering- (1992-)