Isospin mixing in /sup 24/Mg

Journal Article · Tue Mar 01 04:00:00 EST 1983 · Phys. Rev. C; (United States)

DOI:https://doi.org/10.1103/PhysRevC.27.1244· OSTI ID:6031914

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

We have used the ..beta..-..gamma.. circular polarization 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/ = 8.439 MeV. The /sup 24/Al activity was produced by bombarding a natural Mg target with 18 MeV protons. The ..beta..-..gamma.. circular polarization correlation was measured using a novel apparatus which featured good energy resolution in both the ..gamma.. and ..beta.. arms. The circular polarization 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.. circular polarization asymmetry A (defined by W(theta,tau) = 1+tauv/cA costheta where tau is the photon helicity) was found to be A = -0.145 +- 0.030. After applying a correction for feeding of the 8.439 MeV state from the analog state this value of A corresponds to a charge dependent matrix element between the 9.5 MeV 4/sup +/ T = 1 and 8.4 MeV T = 0 levels of Vertical Bar<4/sup +/;0Vertical BarH/sub CD/Vertical Bar4+;1>Vertical Bar = 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 = 0 states have very similar space and spin wave functions. This matrix element is consistent with predictions which ascribe the entire effect to Coulomb forces.

• Research Organization: Nuclear Physics Laboratory, University of Washington, Seattle, Washington 98195
• OSTI ID: 6031914
• Journal Information: Phys. Rev. C; (United States), Journal Name: Phys. Rev. C; (United States) Vol. 27:3; ISSN PRVCA
• 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
ELECTROMAGNETIC RADIATION
ENERGY LEVELS
EVEN-EVEN NUCLEI
FUNCTIONS
GAMMA RADIATION
HADRON REACTIONS
IONIZING RADIATIONS
ISOSPIN
ISOTOPES
LIGHT NUCLEI
MAGNESIUM 24
MAGNESIUM 24 TARGET
MAGNESIUM ISOTOPES
MATRIX ELEMENTS
NUCLEAR REACTIONS
NUCLEI
NUCLEON REACTIONS
ODD-ODD NUCLEI
PARTICLE PROPERTIES
POLARIZATION
PROTON REACTIONS
RADIATIONS
RADIOISOTOPES
SECONDS LIVING RADIOISOTOPES
STABLE ISOTOPES
TARGETS
WAVE FUNCTIONS