UV pumping of hyperfine transitions in the light elements, with application to 21-cm hydrogen and 92-cm deuterium lines from the early universe

摘要

We present new analytic calculations of the coupling between ultravioletresonance photons and the population of the hyperfine states in the lightelements (H, D, He3+) which include several previously neglected physicalprocesses. Among these are the backreaction of resonant scattering on thepumping radiation, the scattering of Ly_beta photons and the effect of localdeparture from pure Hubble flow. The application of the new treatment to theredshifted hydrogen 21 and deuterium 92 cm lines from the high-redshiftuniverse results in an amplitude correction of up to an order of magnitude. Wefurther show that the standard assumption that ultraviolet pumping drives thespin temperature towards the kinetic temperature does not hold for deuterium,whose spin temperature is generally negative.