Isospin mixing in /sup 24/Mg

Technical Report · Fri Jan 01 04:00:00 EST 1982

OSTI ID:6572874

Hoyle, C D; Adelberger, E G; Blair, J S; Snover, K A; Swanson, H E; Von Lintig, R D

We have used the ..beta..-..gamma.. circular polarization (CP) correlation technique to measure the isospin-forbidden Fermi matrix element for the ..beta../sup +/ decay of /sup 24/Al to the 4/sup +/ T=1 state in /sup 24/Mg at E/sub x/=8.437 MeV. The /sup 24/Al activity was produced by bombarding a natural Mg target with 18 MeV protons. The ..beta..-..gamma.. CP correlation was measured using a novel apparatus which featured good energy resolution in both the ..gamma.. and ..beta.. arms. The CP sensitive ..gamma..-ray detector utilized a transmission-mode Compton polarimeter and a 12.7 cm x 15.2 cm NaI detector. The ..beta.. detector was a telescope with a 700 ..mu..m surface barrier detector and a 5.1 cm x 12.7 cm plastic scintillator. The ..beta..-..gamma.. CP asymmetry A (defined by W(theta, t tilde) = 1 + t tilde v/c A tilde cos theta where t tilde is the photon helicity) was found to be A tilde = -0.145 +- 0.030. After applying a correction for feeding of the 8.437 MeV state from the analog state this value of A tilde corresponds to a charge dependent matrix element between the 9.5 MeV 4/sup +/T=1 and 8.4 MeV T=O levels of (<4/sup +/;O(H/sub CD/)4/sup +/;1>) = 106 +- 40 keV which is the largest matrix element of H/sub CD/ ever observed in ..beta.. decay. For comparison the charge dependent matrix element between the 9.5 MeV state and the 4.1 MeV 4/sup +/ state, previously measured in /sup 24/Na decays is only 5.4 +- 2.2 keV. Our exceptionally large value occurs because the 9.5 MeV T=1 and 8.4 MeV T=O states have very similar space and spin wavefunctions. This matrix element is consistent with predictions which ascribe the entire effect to Coulomb forces.

• Research Organization: Washington Univ., Seattle (USA). Nuclear Physics Lab.
• DOE Contract Number: AC06-81ER40048
• OSTI ID: 6572874
• Report Number(s): DOE/ER/40048-25-L2; ON: DE83004920
• Country of Publication: United States
• Language: English

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73 NUCLEAR PHYSICS AND RADIATION PHYSICS
ALKALINE EARTH ISOTOPES
ALUMINIUM 24
ALUMINIUM ISOTOPES
BARYON REACTIONS
BETA DECAY
BETA DECAY RADIOISOTOPES
BETA-PLUS DECAY
BETA-PLUS DECAY RADIOISOTOPES
CHARGE-EXCHANGE REACTIONS
CHARGED-PARTICLE REACTIONS
DECAY
ENERGY-LEVEL TRANSITIONS
EVEN-EVEN NUCLEI
FORBIDDEN TRANSITIONS
HADRON REACTIONS
ISOSPIN
ISOTOPES
LIGHT NUCLEI
MAGNESIUM 24
MAGNESIUM 24 TARGET
MAGNESIUM ISOTOPES
MATRIX ELEMENTS
MEASURING METHODS
NUCLEAR REACTIONS
NUCLEI
NUCLEON REACTIONS
ODD-ODD NUCLEI
PARTICLE PROPERTIES
POLARIZATION
POLARIZATION-ASYMMETRY RATIO
PROTON REACTIONS
RADIOISOTOPES
SECONDS LIVING RADIOISOTOPES
STABLE ISOTOPES
TARGETS
TELESCOPE COUNTERS