Investigation of the electromagnetically induced transparency in the era of cosmological hydrogen recombination

Abstract

Investigation of the cosmic microwave background formation processes is one of the most actual problem at present time. In this paper we analyze the response of the hydrogen atom to the external photon fields. Field characteristics are defined via conditions corresponding to the recombination era of universe. Approximation of three-level atom is used to describe the "atom -fields" interaction. It is found that the phenomena of the electromagnetically induced transparancy (EIT) takes place in this case. Consideration of EIT phenomena makes it necessary to update astrophysical description of the processes of the cosmic microwave background formation and, in particular, Sobolev escape probability. Additional terms to the optical depth entering in the Sobolev escape probability are found to contribute on the level about 1%.

Analysis of the absorption line profile at 21 cm for the hydrogen atom in the interstellar medium

“…Recently, the density matrix formalism was applied to study the effect of Electromagnetically-Induced Transparency (EIT) in hydrogen atom under the conditions corresponding to the recombination era of the universe [7,8]. It was shown that the EIT phenomenon could lead to corrections on the order of 1% in the observed cosmic microwave background (CMB).…”

EIT phenomenon for the three-level hydrogen atoms and its application to the era of cosmological recombination

“…Velocity selection arises because the sensitivity to Doppler shift is weak (LTE principle), Doppler reduction of frequency for the one of photons is compensated by the corresponding increase of frequency for other one. Recently, it was shown also that the EIT phenomenon should be taken into account by means of upgrade of the Sobolev escape probability [6]. In accordance to [4], the Sobolev optical depth should be defined in terms of the Einstein coefficients.…”

“…Recently the cascade 1s − 2p − 3s scheme for the hydrogen atom was considered [6]. It was shown that in the case of exact resonances (when both detunings ∆ p and ∆ c are equal to zero) the maximal value of the f , Eqs.…”

“…However, the presence of external field can bring about effects of the next order (see below) since it changes the medium characteristics, the absorption in particular. In [6] it was demonstrated that the function f is added to the optical depth τ S when the EIT phenomenon is taken into account. It was shown that the contribution to the photon escape probability can reach a level of 1.5%.…”

“…Similarly to [6], but with a larger set of schemes, we use the three-level approximation for the description of the EIT phenomenon in the recombination era of the early universe. We consider the hydrogen atom having a set of ground and two excited states corresponding to the principal quantum number n ≤ 3.…”