Collisions of Alpha-Particles with Neon Nuclei

Abstract

The tracks of more than 700,000 alpha-particles from a source of thorium active deposit have been photographed in a Wilson chamber filled with a mixture of approximately 85 percent neon, 10 percent air, and 5 percent hydrogen. The collisions with nuclei have been studied by replacing the film in the camera and projecting; convenient methods for doing this are described. A range-velocity curve for neon recoil atoms has been constructed by plotting the measured ranges against the calculated velocities for 85 forks. No interactions have been observed which give any evidence of the disintegrations of nuclei, with the emission of protons or neutrons. From a particular study of six elastic, coplanar collisions in which high energies have been transferred to the recoil atoms, it is concluded that the probability of disintegrating ${\mathrm{Ne}}^{20}$ with alpha-particles of less than 6-cm range (in air) is small; from this a lower limit for the mass of ${\mathrm{Na}}^{23}$ is calculated. The methods of measurement and calculation have been thoroughly tested by applying them to collisions with other nuclei, three with hydrogen, five with "air," one with helium, and one with deuterium.