On the Detectability of the Hydrogen 3-cm Fine Structure Line from the EoR (2008)
Dijkstra, Mark, Lidz, Adam, Pritchard, Jonathan R., Greenhill, Lincoln J., Mitchell, D. A., Ord, S. M., ...
A soft ultraviolet radiation field, 10.2 eV < E 2p_3/2) against the Cosmic Microwave Background out to very high redshifts. In particular, the optical depth in the fine-structure line through...