  In this paper we explore the potential effects of DM annihilations on the
cosmological recombination spectrum. With this example we want to demonstrate
that the cosmological recombination spectrum in principle is sensitive to
details related to possible extra energy release during recombination. We
restrict ourselves to DM models which produce a negligible primordial
distortion of the CMB energy spectrum. However, since during the epoch of
cosmological recombination a large fraction of the deposited energy can
directly go into ionizations and excitations of neutral atoms, both the
cosmological recombination spectrum and ionization history can still be
affected significantly. We compute the modifications to the cosmological
recombination spectrum using our multi-level HI and HeI recombination code,
showing that additional photons are created due to uncompensated loops of
transitions which are induced by DM annihilations. As we illustrate here, the
results depend on the detailed branching of the deposited energy into heating,
ionizations and excitations. This dependence in principle should allow us to
shed light on the nature of the underlying annihilating DM model (or more
generally speaking, the mechanism leading to energy injection) when measuring
the cosmological recombination spectrum. However, for current upper limits on
the potential DM annihilation rate during recombination the cosmological
recombination spectrum is only affected at the level of a few percent.
Nevertheless, we argue here that the cosmological recombination spectrum would
provide another independent and very direct way of checking for the presence of
sources of extra ionizing or exciting photons at high redshifts. This would
open an new window to possible (non-standard) processes occurring (abridged)
