
The role of quantum tunneling of hydrogen atoms in the formation of dihydrogen in space is investigated. In their Communication (DOI: 10.1002/anie.201001311) T. P. M. Goumans and J. Kstner use a novel implementation of harmonic quantum transition-state theory to study the reaction rate of hydrogen atoms with benzene. This model of the rate-limiting step of H2 formation on carbonaceous dust grains in space shows that hydrogen reacts about two orders of magnitude faster than the heavier deuterium. Background image: NASA/JPL-Caltech/STScI/CXC/UofA/ESA/AURA/JHU.