Vacuum level

The vacuum level is the potential energy of a particle in a box, which is under vacuum. It should not be confused with the vacuum energy, the energy of " empty space " in the complete absence of particles and fields.

Charged particles

In an electric field

A charged particle in the electric field, the level of vacuum is equal to the product of the electric charge of the particle, with the electrostatic potential of the field in a vacuum:

For electrically conducting solids, such as metals, the vacuum level is also the difference between work function and Fermi energy:

The Fermi energy is usually determined by an electrical contact, which results in the vacuum level.

It follows that an electric field is generated even without an external field between two interconnected conductive bodies, which have different work functions ( about spatial variations of the vacuum level and the electrostatic potential ):

This phenomenon has been previously described with the term contact voltage or contact potential.

Without an electric field

When the room, however, free from electric fields is:

As the electrostatic potential and therefore, the vacuum level is spatially constant:

Atomic physics

In atomic physics, the vacuum level as a reference level for specifying the binding energy of the electrons; this is therefore the minimum necessary energy to bring an electron from its bound state to an atom or molecule on the vacuum level (i.e., in vacuum ). Receives the electron energy, it receives an additional kinetic energy.