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-H2 dimer, we show that simultaneous ionization and excitation of the helium atom induces H2 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 H2 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.