The European Physical Journal C

Velocity effect on the stimulated transition process of a multilevel atom in a thermal bath

Huabing Cai

Published Jul 1, 2021• 6 citations

Abstract

Abstract This paper investigates the stimulated transition process of a uniformly moving atom in interaction with a thermal bath of the quantum electromagnetic field. Using the perturbation theory, the atomic stimulated emission and absorption rates are calculated. The results indicate that the atomic transition rates depend crucially on the atomic velocity, the temperature of the thermal bath, and the atomic polarizability. As these factors change, the atomic stimulated transition processes can be enhanced or weakened at different degrees. In particular, slowly moving atoms in the thermal bath with high temperature ( $$T\gg \omega _{0}$$ T ≫ ω 0 ) perceive a smaller effective temperature $$T \big ( 1-\frac{1}{10} v^{2} \big )$$ T ( 1 - 1 10 v 2 ) for the polarizability perpendicular to the atomic velocity or $$T \big ( 1-\frac{3}{10} v^{2} \big )$$ T ( 1 - 3 10 v 2 ) for the polarizability parallel to the atomic velocity. However, ultra-relativistic atoms perceive no influence of the background thermal bath. In turn, in terms of the atomic transition rates, this paper explores and examines the relativity of temperature of the quantum electromagnetic field.

DOI: 10.1140/epjc/s10052-021-09477-y

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The European Physical Journal C

Velocity effect on the stimulated transition process of a multilevel atom in a thermal bath

Huabing Cai

Published Jul 1, 2021• 6 citations

Publisher

Abstract

T\gg \omega _{0}

T ≫ ω 0 ) perceive a smaller effective temperature

T \big ( 1-\frac{1}{10} v^{2} \big )

T ( 1 - 1 10 v 2 ) for the polarizability perpendicular to the atomic velocity or

T \big ( 1-\frac{3}{10} v^{2} \big )

T ( 1 - 3 10 v 2 ) for the polarizability parallel to the atomic velocity. However, ultra-relativistic atoms perceive no influence of the background thermal bath. In turn, in terms of the atomic transition rates, this paper explores and examines the relativity of temperature of the quantum electromagnetic field.

DOI: 10.1140/epjc/s10052-021-09477-y

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T\gg \omega _{0}

T ≫ ω 0 ) perceive a smaller effective temperature

T \big ( 1-\frac{1}{10} v^{2} \big )

T ( 1 - 1 10 v 2 ) for the polarizability perpendicular to the atomic velocity or

T \big ( 1-\frac{3}{10} v^{2} \big )

T_U=\frac{a}{2\pi }

T U = a 2 π . We discuss in this paper whether there exists such an equivalence in the electromagnetic field case if more atoms are involved. To be specific, we explore the similarities and distinctions between effects of a thermal bath and those of the uniformly accelerated motion by comparing the transition rates of a two-atom system initially in the symmetric or antisymmetric entangled state [

|\psi _{\pm }\rangle

| ψ ± ⟩ ] in two cases, i.e., two static atoms in a thermal bath [the thermal case] and two atoms uniformly accelerated in vacuum [the acceleration case]. We discover that, for some particular orientations of atomic dipole moments, coherent radiation which happens in the acceleration case never occurs in the thermal case. The rates in the acceleration case with a low acceleration which means a low

T_U

T U can be smaller or larger and even equal to their counterparts in the thermal case; while the rates in the acceleration case with a high acceleration which means a high

T_U

T U are always much larger than their counterparts in the thermal case. Our results suggest that effects of a thermal bath and those of the uniformly accelerated motion on transition properties of a two-atom system in

|\psi _{\pm }\rangle

| ψ ± ⟩ are not necessarily distinctive, but can be equivalent if the acceleration is relatively low, depending on the value of the interatomic separation.