Virtual States

in quantum theory, short-lived inter-mediate states of a microsystem in which the usual link between the energy, momentum, and mass of the system is disrupted. The average lifetime of virtual states is on the order of h/Δδ, where Δδ is the deviation of the energy δ from its value as determined by the relations δ= p²/2m₀ in nonrelativistic theory and δ² = c²p²+c⁴m²₀ in relativistic theory, p is the momentum, m₀ is the mass of the system, c is the speed of light, and h is Planck’s constant divided by 2π.

The most important particular case of virtual states is the state of one or more virtual particles. Virtual states usually arise as intermediate states upon the collision of microscopic particles. For example, the collision of neutrons with protons at energies of up to 10-20 mega electron volts takes place essentially by means of the formation and rapid decay of a deuteron in a virtual state.