Minimal theory of isomerism-Q.Q and other interactions

We perform shell model calculations using a quadrupole-quadrupole interaction (Q.Q) in a single j shell space. We show that this one-parameter interaction is a good predictor of where nuclear isomerism occurs and where it does not occur. The limitations of this interaction are also discussed. We then include other interactions, e.g. in the shell those obtained from the (local) spectrum of a two particle system and then from a two hole system. In the where there is insufficient empirical data from the two hole system and so various empirical interactions are used.