Spontaneous fission and $\alpha$ decay from $K$-isomeric states within a cluster approach

Spontaneous fission and $\alpha$ decay from $K$-isomeric states are studied within the dinuclear system model. All these processes are considered as evolution of a nucleus in the charge (mass) asymmetry coordinate. For even-even and even-odd actinides and superheavy nuclei, the spontaneous fission and $\alpha$-decay half-lives of $K$-isomeric states are calculated and compared with the available experimental data. The origin of the hindrance of spontaneous fission from the high-$K$ isomeric states is explained.