Perturbed-angular-correlation measurement of a Fermi to Gamow-Teller mixing ratio in theβdecay ofO19

Time-differential

β - γ

angular correlations perturbed by the nuclear quadrupole interaction in a zinc single crystal were used to extract a value of

y = + 0.030 \pm 0.015

for the ratio

\frac{C_{V} M_{F}}{C_{A} M_{GT}}

of Fermi to Gamow-Teller matrix elements in the allowed

β^{-}

decay from the

\frac{5}{2^{+}}

{}^{19}O

ground state to the

\frac{5}{2^{+}}

, 197 keV state in

{}^{19}F

. This leads to a figure of

M_{F} = (4.7 \pm 2.4) \times 10^{- 3}

for the isospin-forbidden Fermi matrix element. Other parameters which can be derived from this number are

α = (2.7 \pm 1.4) \times 10^{- 3}

for the admixture of the analog of the

{}^{19}O

ground state in the

{}^{19}F

excited state and

| H_{CD} | = 20 \pm 10

keV for the effective charge-dependent matrix element. A value of

ω_{0} = + 8.5 \pm 0.5

\sec^{- 1}

was determined for the nuclear quadrupole interaction of the

{}^{19}F

excited state in a zinc single crystal. The calibration provided by the pure Gamow-Teller decay to the

\frac{3}{2^{+}}

1.554 keV state in

{}^{19}F

was used to remove effects of the implantation process, and data analysis was performed with a model which incorporated the effects of

β' s

backscattered by the thick crystal.

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