A Note on Isotropy in Nuclear Gamma-Radiation

The question of the possibility of competing radiations exhibiting different angular distributions (in the sense that one radiation is isotropic and another anisotropic) is investigated. Except for the singular cases $\frac{3}{2}\to \frac{3}{2}$ and 5→4 by quadrupole emission, our conclusion is as follows: if one radiation of multipole order $2^L$ is observed to be isotropic, all competing gamma-radiation will be isotropic if $L\ge j-\frac{1}{2}$, where $j$ is the angular momentum of the emitting state. The possibility of occurrence of singular cases, for which the conclusion would not apply, has been investigated for all radiations for which $L\le 3$. In the case $\frac{3}{2}\to \frac{3}{2}$, $L=2\mathrm{}$ the radiation is isotropic and the applicability of this to the problem of the excited state of ${\mathrm{Li}}^7$ is briefly discussed.