Kapitsa–Dirac effect

The Kapitsa–Dirac effect is a weird effect that happens when you place a particle with a negative charge like an electron near ajagged or irregular surface. The electron's motion can almost stop, or become extremely slow, by getting stuck in a kind of "pocket" created by the surface. This kind of "pocket" is called an energy valley, and the electron can stay in the same place for a long time. It's like the negative charge of the electron is stuck in the energy valley, even though it's trying to move. Scientists first discovered this strange phenomenon in the 1930s, and they named it after the two scientists who figured it out, P.L. Kapitsa and P.A.M. Dirac.