The Masses of the Heavy Isotopes

Radioactive decay data are used to calculate the atomic masses of the heavy isotopes, $A>~202$. The data have been critically surveyed; in some cases they have been supplemented by construction of tentative energy level schemes or by estimates of decay energies. With the adoption of certain assumptions a connection between the different radioactive families is made possible. The masses thus obtained have been tabulated and plotted. Atomic weight 209 on the Weizsaecker-Fermi formula is found to be unsatisfactory for the calculation of the masses, results deviating by as much as 0.020 mass units from those obtained by experimental data if the latter be adjusted to the calculated ones in the region of lead.