Why does alpha decay of polonium 211 last so long?

The long half-life of polonium-211 (about 138 days) can be attributed to its specific nuclear structure and the energy barrier associated with alpha decay. In alpha decay, the nucleus must overcome the Coulomb repulsion between protons and the binding energy of the emitted alpha particle. Polonium-211 has a relatively stable configuration that requires a significant amount of time for the alpha particle to tunnel through this barrier, resulting in its prolonged decay process.