Inner-valence ionized states of atoms and molecules live shorter if these species are embedded in an environment due to the possibility for ultrafast deexcitation known as interatomic Coulombic decay (ICD). In this Letter we show that the lifetime of these ICD active states decreases further when a bridge atom is in proximity to the two interacting monomers. This novel mechanism, termed superexchange ICD, is an electronic correlation effect driven by the efficient energy transfer via virtual states of the bridge atom. The superexchange ICD is discussed in detail on the example of the NeHeNe trimer. We demonstrate that the decay width of the Ne^{+}(2s^{-1})  ^{2}Σ_{g}^{+} resonance increases 6 times in the presence of the He atom at a distance of 4 Å between the two Ne atoms. Using a simple model, we provide a qualitative explanation of the superexchange ICD and we derive analytical expressions for the dependence of the decay width on the distance between the neon atoms.

Interatomic Coulombic decay (ICD) is a mechanism which allows microscopic objects to rapidly exchange energy. When the two objects are distant, the energy transfer between the donor and acceptor species takes place via the exchange of a virtual photon. On the contrary, recent ab initio calculations have revealed that the presence of a third passive species can significantly enhance the ICD rate at short distances due to the effects of electronic wave function overlap and charge transfer states [Phys. Rev. Lett. 119, 083403 (2017)]. Here, we develop a virtual photon description of three-body ICD, showing that a mediator atom can have a significant influence at much larger distances. In this regime, this impact is due to the scattering of virtual photons off the mediator, allowing for simple analytical results and being manifest in a distinct geometry-dependence which includes interference effects. As a striking example, we show that in the retarded regime ICD can be substantially enhanced or suppressed depending on the position of the ICD-inactive object, even if the latter is far from both donor and acceptor species.Interatomic Coulombic decay (ICD) is an ultrafast process by which energy can be transferred between microscopic objects (e.g. atoms, ions, clusters, quantum dots). First predicted just over two decades ago [1], it involves an excited donor species which then decays and transmits sufficient energy to a neighbouring acceptor species that the latter can be ionised. Since most of the excess energy of the donor is spent ejecting an electron from the acceptor, a slow electron is left in the continuum [2]. As well as being one of the experimental signatures of ICD [3], it has been shown that such slow electrons can be damaging in a biological context [4].The ICD rate is an important property in characterisation of the process. However, its computation is a challenging task. Most calculations of ICD rates use techniques adapted from computational quantum chemistry, necessitated by the donor and acceptor species being very closely spaced so that orbital overlap has a dramatic effect on the system [5,6]. However, at slightly larger distances it is possible to use a 'virtual photon approximation' [5]. There, the donor and acceptor are considered as separate objects coupled via the quantised electromagnetic field. This results in a simple analytic expression for the rate that depends on the single-body decay rate of the donor, the photoionisation cross-section of the acceptor and their mutual separation. This expression is often used as a consistency check for the large-distance behaviour of a particular quantum chemical calculation. Furthermore, an analytical formula for the ICD rate provides a simple means to investigate large systems based on the decomposition of the clusters into pairs [7,8].Recently, a type of three-body ICD mechanism known as superexchange was proposed [9]. Based on extensive ab initio calculations, it was shown that the rate of energy transfer can be substantially enhanced in the presence...

Interatomic Coulombic Decay (ICD) is an ultrafast energy transfer process. Via ICD, an excited atom can transfer its excess energy to a neighboring atom which is thus ionized. On the example of NeHeNe cluster, we recently reported [Phys. Rev. Lett. 119, 083403 (2017)] that the total ICD widths are substantially enhanced in the presence of an ICD inactive atom. The enhancement

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.