Of grains and graphite: Simulating interstellar hydrogen formation
(Phys.org) —The process of molecular hydrogen formation is a key factor in astrophysics – specifically in the physics and chemistry of interstellar clouds. An electrically neutral atom containing a single positively charged proton and a single negatively charged electron bound to the nucleus by the Coulomb force, hydrogen is the lightest element and, in its monatomic (unbound single atom) form, known as H1, is the most abundant chemical substance, constituting roughly 75% of the universe's baryonic mass (that is, excluding so-called dark matter and dark energy). Hydrogen formed at an early stage of the universe during expansion, when the temperature dropped enough to reduce the rate of ionization processes and triggered the plasma-neutral phase transition of the primordial gas. This, in turn, decoupled matter from radiation and led to the appearance of the cosmic background radiation.