Spontaneous excitation of an accelerated atom: The contributions of vacuum fluctuations and radiation reaction

Abstract

We consider an atom in interaction with a massless scalar quantum field. We discuss the structure of the rate of variation of the atomic energy for an arbitrary stationary motion of the atom through the quantum vacuum. Our main intention is to identify and to analyze quantitatively the distinct contributions of vacuum fluctuations and radiation reaction to the spontaneous excitation of a uniformly accelerated atom in its ground state. This gives an understanding of the role of the different physical processes underlying the Unruh effect. The atom's evolution into equilibrium and the Einstein coefficients for spontaneous excitation and spontaneous emission are calculated.

Spontaneous absorption of an accelerated hydrogen atom near a conducting plane in vacuum

“…Therefore, it remains interesting to see what happens to the radiation properties of accelerated atoms found in Ref. [7] when the vacuum fluctuations are further modified by the presence of boundaries. Recently the effects of modified vacuum fluctuations and radiation reaction due to the presence of a conducting plane boundary upon the spontaneous excitation of both an inertial and a uniformly accelerated atom interacting with a quantized real massless scalar field have been discussed [23].…”

“…II, a review of the general formalism developed in Ref. [7] and generalized in Ref. [24,25] to the case of a multi-level atom interacting with a quantized electromagnetic field in the multipolar coupling scheme, then apply it to the case of an inertial atom in Sec.…”

Spontaneous excitation of an accelerated hydrogen atom coupled with electromagnetic vacuum fluctuations

“…[6] to evaluate vacuum fluctuations and radiation reaction contributions to the spontaneous excitation rate [7] and radiative energy shifts [8] of an accelerated two-level atom interacting with a scalar field in a Minkowski vacuum. In particular, their results show that when the atom is accelerated, the delicate balance between vacuum fluctuations and radiation reaction is altered since the contribution of vacuum fluctuations to the rate of change of the mean excitation energy is modified while that of the radiation reaction remains the same.…”

“…Thus transitions to excited states for ground-state atoms become possible even in vacuum. Based upon the formalism developed by Audretsch and Müller [7], the effects of modified vacuum fluctuations and radiation reaction due to the presence of a reflecting plane boundary upon the spontaneous excitation of both an inertial and a uniformly accelerated atom interacting with a quantized real massless scalar field have recently been discussed and similar conclusions are reached [9]. However, a two-level atom interacting with a scalar field is more or less a toy model, and a more realistic system would be a multi-level atom, a hydrogen atom, for instance, in interaction with a quantized electromagnetic field.…”

Geometric phase outside a Schwarzschild black hole and the Hawking effect

“…H φ is the Hamiltonian of the scalar field, whose explicit expression is not required here. We couple the atom and the scalar field by analogy with the electric dipole interaction [31] …”