Virtual Photon Approximation for Three-Body Interatomic Coulombic Decay

Abstract

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...

Interparticle Coulombic Decay Dynamics along Single- and Double-Ionization Pathways

“…With having established here three-electron dynamics MCTDH calculations in QDs, the wealth of other three-and more-electron processes in assemblies of QDs is within reach and will allow for further predictions, e.g. of superexchange ICD 33,34 or the inverse process to this one here, [35][36][37] for all relevant energetic cases. One other systematic improvement of the methodology has been recently achieved, which is the description of a two-dimensional continuum in the electron dynamics 32 reflecting thus self-assembled 38,39 and lithographic QD.…”

Resonance Energy Transfer: From Fundamental Theory to Recent Applications

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Mechanism of superexchange interatomic Coulombic decay in rare-gas clusters

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