QED model of the radiation escape from the matter
  A simple model based on QED is presented for the estimation of contribution of the excited level few-photon decays to the radiation escape from the matter in the epoch of the cosmological hydrogen recombination. It is shown that apart from the widely studied two-photon decays, some specific 3-photon decays can contribute on the level of 0.1% accuracy, required by the recent astrophysical observations. 
T. Zalialiutdinov, D. Solovyev and L. Labzowsky
physics.atom-ph astro-ph.CO