Beta-Gamma Angular Correlation Measurements onAu198. I. Directional and Circular Polarization Correlation

The beta-gamma directional correlation of ${\mathrm{Au}}^{198}$ has been measured as a function of the energy of the beta-particles. The anisotropy factor $A_2\mathrm{}\left(W\right)\mathrm{}$ in the beta-gamma directional correlation ${\mathcal{W}}_{\beta \gamma }(\theta , W)=1+A_2\mathrm{}\left(W\right)\mathrm{}{P}_2\left(cos\theta \right)$ is proportional to $\frac{p^2}{W}$ and its value near the maximum beta energy is $A_2\mathrm{}\left(2.8\right)=0.029\mathrm{}\pm 0.001$. The beta directional gamma circular polarization correlation of ${\mathrm{Au}}^{198}$ was measured using the backscattering of the circularly polarized gamma radiation from a radially magnetized iron disk. The correlation is of the form: ${\mathcal{W}}_{\beta \gamma \mathrm{pol}}(\theta , W)=1+(0.45\mathrm{}\pm 0.07)\left(\frac{p}{W}\right)P_1\left(cos\theta \right)$. The shape correction factor of the first-forbidden beta spectrum is independent of the beta energy above $W=1.6\mathrm{}$ within 5%.