An evaluation of the effect of the dissociative attachment of vibrationally excited H2 on primordial universe chemistry

Abstract

Aims. We study the relevance of including vibrational levels of molecular hydrogen in one of the processes taking place in the primordial Universe: the dissociative attachment of H2. Methods. We calculated the rate of dissociative attachment of H2, covering the contribution of all vibrational levels in standard conditions for primordial Universe chemistry. We then compared this rate to the rates of other chemical processes relevant for H2 balance as a function of z. Results. It is shown that vibrationally excited levels of molecular hydrogen cannot be neglected in evaluating the rate of dissociative attachment in early Universe conditions and that this process is one of the most relevant channels for destruction of H 2 molecules at z ≈ 103. We also propose a preliminary estimation of the effect of a possible non-equilibrium vibrational distribution on the results. © ESO 2007.