AbstractsPhysics

In view of a revival of interest in nuclear physics at McGill and in anticipation of the building of a cyclotron, a program of construction of auxiliary apparatus was started in 1936, in which the writer took part. Delays in the progress of the cyclotron scheme led to the suggestion that some project be undertaken using naturally radioactive sources. The appearance of the work of Bohr on the nature of nuclear reactions indicated that the scattering of alpha particles by the light nuclei might be expected to provide more immediate information concerning nuclear structure than had hitherto been supposed. These considerations led the writer to select the large angle scattering of alpha particles by light nuclei as a subject for experiment. [...] Using a scattering chamber filled with hydrogen at 10 cm. pressure, designed to permit the counting of alpha particles scattered through angles up to 158º, the number scattered into a given solid angle has been compared with the corresponding number from a gold target. Assuming that the latter obeyed Rutherford's law of scattering, the departures from this law in the case of the light elements could, thus, be found. [...] Clear evidence was found in carbon and oxygen for the existence of resonance levels in the compound nuclei formed and it was possible to draw from the data some conclusions regarding the angular momenta of these excited states. [...]