  The cosmological recombination of H and He at z \sim 1000 and the formation
of H2 during the dark ages produce a non-thermal photon excess in the Wien tail
of the cosmic microwave background (CMB) blackbody spectrum. Here we compute
the effect of these photons on the H- photodetachment and H2+ photodissociation
processes. We discuss the implications for the chemical evolution of the
Universe in the post-recombination epoch, emphasizing how important a detailed
account of the full vibrational manifold of H2 and H2+ in the chemical network
is. We find that the final abundances of H2, H2+, H3+ and HD are significantly
smaller than in previous calculations that neglected the effect of non-thermal
photons. The suppression is mainly caused by extra hydrogen recombination
photons and could affect the formation rate of first stars. We provide simple
analytical approximations for the relevant rate coefficients and briefly
discuss the additional effect of dark matter annihilation on the considered
reaction rates.
