Nuclear Matrix Elements of the 437-keV Beta Transition in the Decay ofSb125

The energy dependance of the 437-keV $\beta$—176-keV $\gamma$ directional correlation is measured with a conventional slow-fast scintillation assembly. The results are in good agreement with those of Dubard et al. The matrix-element parameters of this $\beta$ transition are determined using the present results and the allowed shape of the $\beta$ spectrum. The matrix-element parameters indicate that an algebraic cancellation among rank-1 matrix elements is responsible for the retardation of the 437-keV $\beta$ transition. The ratio of the matrix elements $\int \overrightarrow{\alpha }$ and $\int i\overrightarrow{\mathrm{r}}$ is not in agreement with the value predicted on the basis of conserved-vector-current theory.