Electron-Neutrino Angular Correlation in the Beta-Decay ofHe6

The recoil nuclei emitted during the beta-decay of ${\mathrm{He}}^6$ have been detected by means of an electron multiplier tube, and the beta-rays counted by means of an end window Geiger counter. The energy spectrum of the recoils has been studied by recording coincidences between the two detectors as a function of the retarding potential between a set of girds in the path of the recoils. Beta-recoil ion coincidences have been observed when the angle between the directions of emission of the beta-particle and of the recoil ion was 180 degrees and also 162 degrees. In both cases the best agreement was obtained when the recoil spectra were compared with the curves predicted by the $1-\left(\frac{v}{3c}\right)cos\theta$ electron-neutrino angular correlation.