A Nonperturbative Treatment of Spin Dependent Interactions of Light and Heavy Quarkonia

We propose a nonrelativistic potential model with a regularized Coulomb potential at short range which leads to spindependent interactions which are at most as singular as 1/r. The Schrödinger equation is solved numerically including all spin-dependent interactions nonperturbatively. The predicted spectrum of light and heavy quarkonia is in remarkable agreement with experiment. Even the leptonicdecay widths as well as theM1 transitions are in agreement with experiment.