Differentiability of the energy surfaces of even–even nuclei

The expansion of even–even nucleus energy in power series of deviations from the given values of neutron and proton numbers. The calculation of the expansion parameters up to the sixth order shows that the values of parameters are sensible to the choice of the group of nuclei used for the calculation. This indicates that the nuclear energy surface is not sufficiently smooth (or completely differentiable). It is shown that the expression proposed earlier by the authors for the pairing energy of an odd nucleus in a definite quantum state does not need to be refined and can be used for the subsequent analysis of pairing energies.