A basic quantity which can be measured for the ground states of nuclei is the atomic mass \( M(N, Z) \) of the neutral atom with atomic mass number \( A \) and charge \( Z \). The number of neutrons is \( N \).

Atomic masses are usually tabulated in terms of the mass excess defined by $$ \Delta M(N, Z) = M(N, Z) - uA, $$ where \( u \) is the Atomic Mass Unit $$ u = M(^{12}\mathrm{C})/12 = 931.49386 \hspace{0.1cm} \mathrm{MeV}/c^2. $$ In this course we will mainly use data from the 2003 compilation of Audi, Wapstra and Thibault.