Progress toward the $\mathcal{P}$, $\mathcal{T}$-odd Faraday effect: Light absorption by atoms briefly interacting with a laser beam

Abstract

We investigate the process of photon absorption by atoms or molecules shortly interacting with a laser beam in the dipole approximation. Assuming that the interaction time $τ$ is much smaller than the lifetime of the corresponding excited state, we examine the absorption probability as a function of $τ$. Besides, we incorporate Doppler broadening due to nonzero temperature of the atoms (molecules). It is demonstrated that in the case of a zero detuning and without Doppler broadening, the absorption probability is quadratic in $τ$. Once Doppler broadening is taken into account or the laser beam is off from the resonant frequency, the absorption probability becomes linear in $τ$. Our findings are expected to be important for experimental studies in optical cells or cavities where atoms or molecules traverse continuous laser beams. The experimental prospects of searching for the electric dipole moment (EDM) of the electron are discussed in detail.