barrier penetration

tunneling

 or barrier penetration

In physics, the passage of a particle through a seemingly impassable energy barrier. Though a particle's energy may be too low to surmount a barrier in classical physics, the particle may still cross the barrier as a consequence of its quantum-mechanical wave properties. An important application of this phenomenon is in the operation of the scanning tunneling microscope.

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barrier penetration [′bar·ē·ər ‚pen·ə′trā·shən]

(quantum mechanics)

The passage of a particle through a potential barrier, that is, through a region of finite extent in which the particle's potential energy is greater than its total energy.