Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: UV pumping of hyperfine transitions in the light elements, with
  application to 21-cm hydrogen and 92-cm deuterium lines from the early
  universe   We present new analytic calculations of the coupling between ultraviolet
resonance photons and the population of the hyperfine states in the light
elements (H, D, He3+) which include several previously neglected physical
processes. Among these are the backreaction of resonant scattering on the
pumping radiation, the scattering of Ly_beta photons and the effect of local
departure from pure Hubble flow. The application of the new treatment to the
redshifted hydrogen 21 and deuterium 92 cm lines from the high-redshift
universe results in an amplitude correction of up to an order of magnitude. We
further show that the standard assumption that ultraviolet pumping drives the
spin temperature towards the kinetic temperature does not hold for deuterium,
whose spin temperature is generally negative.

8
The categories of this paper are: hep-ex
32
The categories of this paper are: atom-ph
26
The categories of this paper are: bayes-an
20
The categories of this paper are: acc-phys
19
The categories of this paper are: eess
24
The categories of this paper are: dg-ga
22
The categories of this paper are: chao-dyn
1
The categories of this paper are: cs
2
The categories of this paper are: math
4
The categories of this paper are: cond-mat
36
The categories of this paper are: cmp-lg
7
The categories of this paper are: hep-th
30
The categories of this paper are: q-alg
10
The categories of this paper are: q-bio
12
The categories of this paper are: nucl-th
21
The categories of this paper are: adap-org