In a survey for alpha-activity among cyclotron produced neutron deficient nuclides of the elements below lead, alpha-activity was detected in a number of rare earth nuclides with atomic number greater than 62, that of samarium, and in a gold and a mercury nuclide. A detailed study of the alpha-active nuclides of europium, gadolinium, terbium, and dysprosium was made.

The relationship between alpha-decay rates and energies in the rare earth region is examined. Calculations of the "effective nuclear radius for alpha-particles" were made using five different alpha-decay rate formulas.

The trends of the rare earth alpha-decay energies are discussed, particularly with respect to the discontinuity in neutron binding energies at the closed shell of 82 neutrons.

• Received 15 September 1952

DOI:https://doi.org/10.1103/PhysRev.89.33