摘要: Laboratory studies on the interaction of atomic hydrogen with aliphatic and aromatic hydrogenated carbon grains are discussed. When exposed to hydrogen, both types act as catalysts for molecular formation. In first case, an exchange reaction chemisorbed in sites is formation route H 2 For grains, takes place through a two-step sequence: 1) super hydrogenation islands 2) reactions these islands. This mechanism represents good approximation large neutral PAHs.