Beta-Gamma Directional Correlations inRe186andTm170

The beta-gamma directional correlations have been measured for the (934-keV beta) (137-keV gamma) cascade in ${\mathrm{Re}}^{186}$ and the (883-keV beta) (84-keV gamma) cascade in ${\mathrm{Tm}}^{170}$. The coefficient $A_2$ varies from 0.035 at a beta energy of 220 keV to 0.095 at a beta energy of 830 keV in the case of ${\mathrm{Re}}^{186}$ and varies from -0.055 at a beta energy of 330 keV to -0.090 at a beta energy of 740 keV in the case of ${\mathrm{Tm}}^{170}$. Interpretation of the decays in terms of limitations on the first forbidden beta decay matrix elements is discussed. For ${\mathrm{Re}}^{186}$ the directional correlation and the spectral shape correction can be fitted for values of the parameter [${\zeta }_1$[greater than 2. Rough agreement with the measurement of the beta-circularly polarized gamma correlation is also found. For ${\mathrm{Tm}}^{170}$ the directional correlation and an allowed spectral shape can be fitted for ${\zeta }_1<-2\mathrm{}$ and ${\zeta }_1>20\mathrm{}$.