- a quantum-mechanical process by which a particle can pass through a potential energy barrier that is higher than the energy of the particle: first postulated to explain the escape of alpha particles from atomic nuclei.
- the phenomenon in which an object, usually an elementary particle, tunnels through a potential barrier even though it does not have sufficient energy to surmount the barrier. It is explained by wave mechanics and is the cause of alpha decay, field emission, and certain conduction processes in semiconductors
