Giant dipole resonance in silicon-28

Thesis/Dissertation · Tue Jan 01 04:00:00 EST 1980

OSTI ID:5190128

Gulbranson, R L

In order to provide new insights into the character of the giant dipole resonance in nuclei the photoproton and photoalpha cross sections for /sup 28/Si in the energy region 15.62 through 22.50 MeV were measured with gamma ray resolution of approximately 200 keV using the University of Illinois bremsstrahlung monochromator. A silicon particle detector was used both as a target and as a 4..pi.. solid angle detector for the reaction products. Three detectors were used: an 1 mm surface barrier detector, a 3 mm Si(Li) detector, and a 5 mm Si(Li) detector. All three detectors had an area of 300 mm/sup 2/. The partial cross sections for /sup 28/Si(..gamma..,p) reactions leaving /sup 27/Al in its ground state and first ten excited states were measured. The experimental energy resolution was not adequate to permit the separation of the fifth and sixth excited states or the eighth and ninth excited states. The partial cross sections for /sup 28/Si(..gamma..,..cap alpha..) reactions leaving /sup 24/Mg in its ground state and first two excited states were also measured. The data confirm the fine structure seen in earlier experiments, but do not have the resolution of the earlier inverse reaction experiments which provide information on the ground state decays through detailed balance. The measured partial cross sections were analyzed using the statistical compound nucleus model. The results of this analysis indicate that, for the most part, the protondecays are neither direct nor statistical in nature. The alpha particle decays are most probably statistical in nature. The total photoabsorption cross section for /sup 28/Si shows four major peaks. This general trend is observed in most of the partial cross sections, suggesting that theoretical descriptions of the /sup 28/Si giant dipole resonance, which have invoked differing particle-hole configurations for each of the four major peaks, are incorrect.

• Research Organization: Illinois Univ., Urbana (USA)
• OSTI ID: 5190128
• Country of Publication: United States
• Language: English

Related Subjects

651425* -- Nuclear Properties & Reactions
A=20-38
Experimental-- Nuclear Reactions & Scattering-- (-1987)
73 NUCLEAR PHYSICS AND RADIATION PHYSICS
ALKALINE EARTH ISOTOPES
ALPHA PARTICLES
ALUMINIUM 27
ALUMINIUM ISOTOPES
BARYONS
BASIC INTERACTIONS
CHARGED PARTICLES
COMPOUND-NUCLEUS REACTIONS
CROSS SECTIONS
DATA
ELECTROMAGNETIC INTERACTIONS
ELEMENTARY PARTICLES
ENERGY LEVELS
ENERGY RANGE
EVEN-EVEN NUCLEI
EXPERIMENTAL DATA
FERMIONS
GAMMA SPECTRA
GIANT RESONANCE
HADRONS
INFORMATION
INTERACTIONS
ISOTOPES
LIGHT NUCLEI
MAGNESIUM 24
MAGNESIUM ISOTOPES
MATHEMATICAL MODELS
MEV RANGE
MEV RANGE 10-100
NUCLEAR REACTIONS
NUCLEI
NUCLEONS
NUMERICAL DATA
ODD-EVEN NUCLEI
PARTICLE PRODUCTION
PHOTONUCLEAR REACTIONS
PHOTOPRODUCTION
PROTONS
RESONANCE
SILICON 28
SILICON 28 TARGET
SILICON ISOTOPES
SPECTRA
STABLE ISOTOPES
STATISTICAL MODELS
TARGETS