What are the main reasons behind the formation of different kind of isomers in different nuclei?
Nuclear Isomers are like any other excited states but longer lived than the normal excitations. The longer life of these specific states makes them isomer. Long life arises due to hindrance to the decay of these states. Such hindrance may arise due to various reasons. Most common is a large change in the spin while decaying from isomeric state to the final state. These are spin isomers. Other reasons could be a sudden change in the shape (shape and fission isomers), or, change in the orientation of the spin (K-isomers), and finally the seniority isomers which involve a subtle interplay of the seniority among the decaying states. For a detailed discussion, I refer to our book “Nuclear Isomers – A Primer”, Springer, 2021.
