H ₂ Formation on Interstellar Dust Grains: The Viewpoints of Theory, Experiments, Models and Observations

Molecular hydrogen (H ₂ ) is the most abundant molecule in the Universe. Its formation involves catalytic reactions occurring on the surface of interstellar dust grains, but also involving polycyclic aromatic hydrocarbons (PAHs). Experiments and theoretical calculations have been performed to determine the processes governing the...