Molecular-bond breaking induced by interatomic decay processes

Selective bond breaking in a molecule with the use of photons opens the way to control chemical reactions. We demonstrate here that dissociation of a molecule can be efficiently achieved by first photoexciting a neighboring atom or molecule. On the example of the giant He-H-2 dimer, we show that simultaneous ionization and excitation of the helium atom induces H-2 dissociation with a high probability. The excited He+ ion transfers its excess energy via interatomic Coulombic decay (ICD) or electron transfer mediated decay (ETMD) to H-2 which is then singly or doubly ionized, respectively. In both cases, the molecular ion dissociates effectively within a few tens of femtoseconds. Molecular-bond breaking induced by ICD and ETMD are expected to be general phenomena, which provide alternatives to standard photochemistry.