ABSTRACT
Many nuclear properties are explained by assuming that the nucleus is a system of independent particles, moving in an average potential created by all the nucleons. 1·2 This idea of a single-particle motion is the opposite of the collective motion hypothesis governing the liquid drop model. At first sight it is hard to understand how a system of strongly interacting nucleons could behave as if it is made of free or weakly interacting particles, but in fact the mean free path of the nucleons in a nucleus is of the order of the nuclear dimensions, due to the Pauli principle.
