Odd-Even Staggering of Nuclear Masses: Pairing

The odd-even staggering of nuclear masses was recognized in the early days of nuclear physics. Recently, a similar e ect was discovered in other nite fermion systems, such as ultrasmall metallic grains and metal clusters. It is believed that the staggering in nuclei and grains is primarily due to pairing correlations (superconductivity), while in clusters it is caused by the Jahn-Teller e ect. We nd that, for light and medium-mass nuclei, the staggering has two components. The rst one originates from pairing while the second, comparable in magnitude, has its roots in the deformed mean eld.