Helicity of Antineutrinos Emitted by Nuclei

The helicity of antineutrinos emitted in nuclear transitions has been measured by determining the circular polarization of gamma rays emitted by a gaseous source of ${\mathrm{Hg}}^{203}$ and resonantly scattered by ${\mathrm{Tl}}^{203}$ nuclei. The antineutrinos and electrons preceding these gamma rays are known to travel approximately opposite to the gamma quanta. The helicity of neutrinos emitted following electron capture has been remeasured using the same apparatus.