A survey of neutron and proton binding energies

Abstract

Limiting values of last-nucleon binding energies are available from measured reaction energies of induced transformations satisfying the selection rule ΔA=0, ±1 (A=mass number) in about 140 cases. In 14 cases upper and lower limiting values are known separately, and these agree in each case within the limits of experimental error. Taking the other 126 values as ‘true’ (rather than limiting) values, and using information concerning total energies of β-disintegration, the number of last-nucleon binding energies which are reasonably well determined is increased to more than 600. These values are tabulated, and discussed in relation to the v. Weizsäcker mass formula. Apart from certain anomalies which are treated individually, the discussion brings out the effect of α-unit structure in light nuclei, diminishing in importance to become almost negligible beyond A=40, and yields mean values for nucleon-parity dependent terms in the range A∼215. The recovery of ‘normal’ last-nucleon binding energy after completion of a closed shell is followed in detail over the range 126ˇ-Nˇ-136 (N=neutron number) and somewhat less closely over the range 82ˇ-Zˇ-92 (Z=proton number).