SPIN EFFECTS IN HEAVY QUARKONIA

A model based on a nonrelativistic potential supplemented by spin depe ndent terms of the Breit-Fermi type is described. This model reproduce s the known masses of the (b) over bar b quarkonia within 1MeV and the known masses of the (c) over bar c quarkonia within 5MeV. Many predic tions are made, some of them, e.g. for the fine splittings of the high L states of the (b) over bar b quarkonia and of the mass spectrum of the (b) over bar c quarkonia, significantly different from previous pr edictions made by other authors.