Effect of radiative feedbacks for resonant transitions during cosmological recombination

The inhibition of the total HI n <-> 1 transition rate by delayed resonant reabsorption of HI (n + 1) -> 1 photons by HI n -> 1 line which is possible due to cosmological redshift is considered semianalytically. The method taking into account this effect in the frame of simple three-level approximation model of recombination is suggested. It is confirmed that the resonant feedbacks affect ionization fraction at the level about 0.2% for the epoch of last scattering. Similar consideration of HeI 2(1)P <-> 1(1)S double right arrow HeI 2(3)P <-> 1(1)S feedback for helium is provided. It is confirmed that allowance of this feedback leads to an increase of predicted free electron fraction by 0.12% at z similar or equal to 2300. It is shown that taking into account absorption and thermalization of HeI 2(1)P <-> 1(1)S resonant superequilibrium photons (during their redshifting to the HeI 2(3)P <-> 1(1)S frequency) by a small amount of neutral hydrogen (10(-7)-10(-4) of total number of hydrogen atoms and ions) existing in the helium recombination epoch is important for correct consideration of this helium feedback.