Giant resonance in transitional nuclei: Photoneutron cross sections for osmium isotopes

Journal Article · Sun Apr 01 04:00:00 EST 1979 · Phys. Rev., C; (United States)

DOI:https://doi.org/10.1103/PhysRevC.19.1205· OSTI ID:6281660

Berman, B L; Faul, D D; Alvarez, R A; Meyer, P; Olson, D L

Photoneutron cross sections, including sigma((..gamma..,n) + (..gamma..,pn)), sigma((..gamma..,2n) + (..gamma..,p2n)), and sigma (..gamma..,3n), were measured for /sup 188/Os,/sup 189/Os, /sup 190/Os, and /sup 192/Os from 7 to 30 MeV and for /sup 186/Os from 11 to 20 MeV, with a photon energy resolution of about 300 keV. The source of radiation was the monoenergetic photon beam obtained from the annihilation in flight of fast positrons. The partial photoneutron cross sections were determined by neutron multiplicity counting, and the average neutron energies for each multiplicity were determined simultaneously with the cross-section data by the ring-ratio technique. Nuclear information extracted from the data includes parameters of the giant dipole and giant quadrupole resonances, integrated cross sections and their moments, nuclear symmetry energies, and nuclear deformation parameters and intrinsic quadrupole moments. No fewer than eight kinds of evidence point to a sudden change of behavior between /sup 189/Os and /sup 190/Os, which could be interpreted as a phase transition from a statically deformed prolate nucleus to a ..gamma..-unstable one, in general (but not detailed) agreement with the prediction of a dynamic-collective-model calculation.

• Research Organization: Lawrence Livermore Laboratory, University of California, Livermore, California 94550
• OSTI ID: 6281660
• Journal Information: Phys. Rev., C; (United States), Journal Name: Phys. Rev., C; (United States) Vol. 19:4; ISSN PRVCA
• Country of Publication: United States
• Language: English

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73 NUCLEAR PHYSICS AND RADIATION PHYSICS
BARYONS
COLLECTIVE MODEL
CROSS SECTIONS
DEFORMATION
ELEMENTARY PARTICLES
ENERGY RANGE
FERMIONS
GIANT RESONANCE
HADRONS
MATHEMATICAL MODELS
MEV RANGE
MEV RANGE 01-10
MEV RANGE 10-100
MULTIPLICITY
NEUTRONS
NUCLEAR DEFORMATION
NUCLEAR MODELS
NUCLEAR REACTION YIELD
NUCLEAR REACTIONS
NUCLEONS
OSMIUM 186 TARGET
OSMIUM 188 TARGET
OSMIUM 189 TARGET
OSMIUM 190 TARGET
OSMIUM 192 TARGET
PHOTONEUTRONS
PHOTONUCLEAR REACTIONS
PHOTONUCLEONS
QUADRUPOLE MOMENTS
RESONANCE
TARGETS
YIELDS