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

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.