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Physical Review A

Modification of stimulated transition processes of a uniformly moving atom by the presence of a dielectric medium in blackbody radiation

Huabing Cai, Li‐Gang Wang

Published Oct 18, 2023• 2 citations
Publisher

Abstract

We investigate the effect of the presence of a dielectric medium on the stimulated transition processes of a uniformly moving atom in a thermal radiation field. The cases of atomic subluminal and superluminal motions are considered. The calculated results indicate that the atomic stimulated transition rates depend crucially on the atomic velocity, the temperature of the thermal radiation, the refractive index of medium, and the atomic polarizability. The transition rates are expanded by series in some limiting cases, such as the extreme temperature of thermal radiation, the extreme motion of the atom, and the extremely large refractive index. Our analytical and numerical analyses show that the presence of the dielectric medium has profoundly changed the behaviors and characteristics of the atomic stimulated transition rates, especially when the atom moves faster than the speed of light in the medium. Moreover, the behavior of the transition rates for an atom polarized parallel to the direction of atomic motion is quite distinct from that of an atom polarized perpendicularly to the direction of atomic motion.

DOI
10.1103/physreva.108.043715

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We investigate the effect of the presence of a dielectric medium on the stimulated transition processes of a uniformly moving atom in a thermal radiation field. The cases of atomic subluminal and superluminal motions are considered. The calculated results indicate that the atomic stimulated transition rates depend crucially on the atomic velocity, the temperature of the thermal radiation, the refractive index of medium, and the atomic polarizability. The transition rates are expanded by series in some limiting cases, such as the extreme temperature of thermal radiation, the extreme motion of the atom, and the extremely large refractive index. Our analytical and numerical analyses show that the presence of the dielectric medium has profoundly changed the behaviors and characteristics of the atomic stimulated transition rates, especially when the atom moves faster than the speed of light in the medium. Moreover, the behavior of the transition rates for an atom polarized parallel to the direction of atomic motion is quite distinct from that of an atom polarized perpendicularly to the direction of atomic motion.
We investigate the influence of the presence of a dielectric medium on the energy shift for a uniformly moving atom in blackbody radiation. The atomic energy-level shift usually depends on the temperature of thermal radiation, the atomic velocity, the refractive index of the medium, and the atomic polarizability. Analytical and numerical analyses indicate that the presence of the dielectric medium has profoundly disturbed the behavior of the atomic energy shifts, especially when the atomic speed is greater than the speed of light in the medium. Our work further suggests that the combination of a medium and atomic relativistic center-of-mass motion can provide insight into the radiative properties of atom-field coupling system.
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≫ω0T\gg \omega _{0}T≫ω0​ T ≫ ω 0 ) perceive a smaller effective temperature T(1−110v2)T \big ( 1-\frac{1}{10} v^{2} \big )T(1−101​v2) T ( 1 - 1 10 v 2 ) for the polarizability perpendicular to the atomic velocity or T(1−310v2)T \big ( 1-\frac{3}{10} v^{2} \big )T(1−103​v2) 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.
Abstract We investigate the influence of atomic uniform motion on radiative energy shifts of a multilevel atom when it interacts with black-body radiation. Our analysis reveals that the atomic energy shifts depend crucially on three factors: the temperature of black-body thermal radiation, atomic velocity, and atomic polarizability. In the low-temperature limit, the presence of atomic uniform motion always enhances the effect of the thermal field on the atomic energy shifts. However, in the high-temperature limit, the atomic uniform motion enhances the effect of the thermal field for an atom polarizable perpendicular to the atomic velocity but weakens it for an atom polarizable parallel to the atomic velocity. Our work indicates that the physical properties of atom–field coupling systems can in principle be regulated and controlled by the combined action of the thermal field and the atomic uniform motion.
The change in the decay rate of an excited atom that is brought about by extinction and thermal-radiation effects in a nearby dielectric medium is determined from a quantum-mechanical model. The medium is a collection of randomly distributed thermally excited spherical scatterers with absorptive properties. The modification of the decay rate is described by a set of correction functions for which analytical expressions are obtained as sums over contributions from the multipole moments of the scatterers. The results for the modified decay rate as a function of the distance between the excited atom and the dielectric medium show the influence of absorption, scattering and thermal-radiation processes. Some of these processes are found to be mutually counteractive. The changes in the decay rate are compared to those following from an effective-medium theory in which the discrete scatterers are replaced by a continuum.
When a dielectric medium has a finite temperature, the atoms that constitute the medium are in a state of incessant motion. Propagation of a light pulse through such a medium is discussed theoretically in this paper in the classical domain. When the pulse is in resonance with the medium, it is found that the medium becomes dispersiveless when its temperature reaches a critical value, and that as the medium's temperature increases from below to above the critical value, the pulse's propagation changes from superluminal (subluminal) to subluminal (superluminal).