Evolution of the pygmy dipole resonance in Sn isotopes

Journal Article · Fri Apr 15 04:00:00 EDT 2011 · Physical Review. C, Nuclear Physics

DOI:https://doi.org/10.1103/PHYSREVC.83.044320· OSTI ID:21499571

Toft, H K; Larsen, A C; Buerger, A; Guttormsen, M; Goergen, A; Nyhus, H T; Renstroem, T; Siem, S; Tveten, G M ^[1]; Voinov, A ^[2]

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1. Department of Physics, University of Oslo, N-0316 Oslo (Norway)
2. Department of Physics and Astronomy, Ohio University, Athens, Ohio 45701 (United States)

Nuclear level density and {gamma}-ray strength functions of {sup 121,122}Sn below the neutron separation energy are extracted with the Oslo method using the ({sup 3}He,{sup 3}He{sup '{gamma}}) and ({sup 3}He,{alpha}{gamma}) reactions. The level densities of {sup 121,122}Sn display steplike structures, interpreted as signatures of neutron pair breaking. An enhancement in both strength functions, compared to standard models for radiative strength, is observed in our measurements for E{sub {gamma}} > or approx. 5.2 MeV. This enhancement is compatible with pygmy resonances centered at {approx_equal}8.4(1) and {approx_equal}8.6(2) MeV, respectively, and with integrated strengths corresponding to {approx_equal}1.8{sub -5}{sup +1}% of the classical Thomas-Reiche-Kuhn sum rule. Similar resonances were also seen in {sup 116-119}Sn. Experimental neutron-capture cross reactions are well reproduced by our pygmy resonance predictions, while standard strength models are less successful. The evolution as a function of neutron number of the pygmy resonance in {sup 116-122}Sn is described as a clear increase of centroid energy from 8.0(1) to 8.6(2) MeV, but with no observable difference in integrated strengths.

• OSTI ID: 21499571
• Journal Information: Physical Review. C, Nuclear Physics, Journal Name: Physical Review. C, Nuclear Physics Journal Issue: 4 Vol. 83; ISSN 0556-2813; ISSN PRVCAN
• Country of Publication: United States
• Language: English

Related Subjects

73 NUCLEAR PHYSICS AND RADIATION PHYSICS
ALPHA DECAY
BARYON REACTIONS
BARYONS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BINDING ENERGY
CHARGED-PARTICLE REACTIONS
DAYS LIVING RADIOISOTOPES
DECAY
DIPOLES
ELECTROMAGNETIC RADIATION
ELEMENTARY PARTICLES
ENERGY
ENERGY RANGE
ENERGY-LEVEL DENSITY
EQUATIONS
EVEN-EVEN NUCLEI
EVEN-ODD NUCLEI
FERMIONS
FIELD THEORIES
FORECASTING
FUNCTIONS
GAMMA DECAY
GAMMA RADIATION
GRAND UNIFIED THEORY
HADRON REACTIONS
HADRONS
HELIUM 3 REACTIONS
INTERMEDIATE MASS NUCLEI
INTERNAL CONVERSION RADIOISOTOPES
IONIZING RADIATIONS
ISOMERIC TRANSITION ISOTOPES
ISOTOPES
MATHEMATICAL MODELS
MEV RANGE
MEV RANGE 01-10
MULTIPOLES
NEUTRON REACTIONS
NEUTRON SEPARATION ENERGY
NEUTRONS
NUCLEAR DECAY
NUCLEAR REACTIONS
NUCLEI
NUCLEON REACTIONS
NUCLEONS
PARTICLE MODELS
QUANTUM FIELD THEORY
RADIATIONS
RADIOISOTOPES
RESONANCE
STABLE ISOTOPES
STANDARD MODEL
STRENGTH FUNCTIONS
SUM RULES
TIN 116
TIN 117
TIN 118
TIN 119
TIN 120
TIN 121
TIN 122
TIN ISOTOPES
UNIFIED GAUGE MODELS
YEARS LIVING RADIOISOTOPES