Investigation of Higher Order Effects in the Allowed Beta Decay ofMn56

Directional-correlation measurements were performed on the allowed 2.86-MeV $\beta$-0.845-MeV $\gamma$ transition in the decay of ${\mathrm{Mn}}^{56}$. The results indicate that a small negative correlation ($A_2=-0.0030\mathrm{}\pm 0.0011$) exists. For comparison, the $\beta -\gamma$ directional correlation was also measured in the allowed $\beta$ decay of ${\mathrm{I}}^{131}$. The distribution was found to be isotropic within the experimental error and the correlation coefficient was found to be $\left|A_2\right|<\mathrm{}0.0005\mathrm{}$ in this case. The deviation of the ${\mathrm{Mn}}^{56}$ $\beta$ spectrum from allowed shape is discussed and it is shown that a shape factor of the form $C\approx 1+0.04W-\frac{0.01}{W}$ would not be inconsistent with the observed anisotropy.