Nuclear Thermodynamics of the Heaviest Elements

Abstract

The phenomenon of alpha particle emission, a general observable property for the nuclides above lead, makes it possible to relate these nuclides energetically. The radioactive decay energy along a radioactive series can be summed so that the total decay energy for each nuclide in the series is known with respect to its position above teh bottom of the series, that is, with respect to its terminal lead (or bismuth) isotope. This can be done for each of the four mass types and, as shown, one can obtain this information for all the collateral members as well as the members in the main line of decay. Thus it is possible, using the relation between mass and energy and the known mass of the alpha particle, to convert this radioactive decay energy ine ach case to a relative mass value based on the mass of one of the four end products, Pb{sup 208}, Pb{sup 207}, Pb{sup 206}, or Bi{sup 209}. If the absolute mass of each of these is known, it is then possible to calculate the absolute mass for all the heavy nuclides above lead for which decay energy data are known or can be estimated. The absolute mass of only one of this group of four need actually be known since the neutron binding energies related them can be measured. it is also possible to measure the absolute masses of other nuclei in each of the four series, for example, such nuclides as U{sup 238}, Th{sup 232}, U{sup 235}, or Np{sup 237} which are available in sufficient quantity for mass spectrographic measurements, and the aboslute masses of the other members of each of the series may then be calculated from these through proper use of the decay data. if the absolute masses of more than one member of the same mass type is known, it is possible to have a check on the accuracy of the radioactive decay values. Once all the masses of the heavy nuclides are known accurately, it is possible to construct the energy surfaces corresponding to this region and to study the energetics of the heavy region as a whole. The present paper is concerned with the use of the radioactive, neutron-binding and mass spectrographic data for the calculation of the relative and absolute masses of the translead nuclides and the use of these in connection with the energy surface and general energetics of this region.