Further Experiments on the Recoil of the Nucleus in Beta-Decay

Abstract

Experiments on the recoil of the nucleus in the disintegration of ${\mathrm{Cl}}^{38}$ have been continued. The fact (which has been reported in earlier publications) that momentum is not conserved in the system consisting only of the nucleus and the emitted electron has been confirmed. By measuring the momenta of the electron and nucleus it has been possible to ascertain the direction of emission of the neutrino with respect to the direction of the electron in each case. Theoretical predictions according to both the Fermi and the K-U theory are plotted for comparison. The experimental data agree slightly better with the Fermi than with the K-U theory, but it is not safe to attach much significance to the results obtained on this aspect of the problem, because of the possibilities for rather large experimental errors. An investigation into the manner in which droplets in the cloud chamber are produced by the recoil atom has been carried out. Evidence is offered which indicates that the products resulting from dissociation of the gas molecules act as centers for condensation. This effect, in addition to ionization, accounts for the droplets observed.