Confinement Without Walls

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Science  15 Jun 2001:
Vol. 292, Issue 5524, pp. 1967
DOI: 10.1126/science.292.5524.1967b

When particles such as electrons are placed in a confining potential (“box”), they exhibit a discrete ladder of energy levels. An intuitive description involves reflections of waves from walls: These discrete energy levels can be thought of as arising from fitting integer multiple half-wavelengths associated with the electron into the box. However, quantum mechanics dictates that a wall is not necessary for the reflection to occur, but that a simple step jump in the potential would work equally well. In this case, the electrons would be confined to a plateau and would be reflected at the boundary region. Barman et al. deposited a thin layer of sodium atoms on an aluminum substrate to mimic the plateau and step-down potential structure. They observed resonances in the photoemission spectrum that are in agreement with the scenario in which the electron wave functions are indeed reflected from the sodium-aluminum boundary. — ISO

Phys. Rev. Lett. 86, 5108 (2001).

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