Interatomic Coulombic Decay in van der Waals Clusters and Impact of Nuclear Motion

Santra, Robin; Zobeley, Jürgen; Cederbaum, Lorenz S.; Moiseyev, Nimrod

doi:10.1103/physrevlett.85.4490

Cited by 167 publications

(148 citation statements)

References 21 publications

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“…Traditionally, it is assumed that in extended aggregates -molecules or bulk matter-electrons only at the excited site actively take part in the decay and that the environment of the initially excited atom only modifies the Auger energy spectrum via its influence on the energy levels [1][2][3]. In contrast to that, for weakly bound aggregates, such as van der Waals clusters and hydrogen bonded systems, a radiationless decay mechanism has been predicted, which is possible only by electron emission from neighboring sites of the vacancy [4][5][6]. The final states populated in this so-called ''interatomic Coulombic decay'' (ICD) thus have two positive charges distributed at two different atoms of the system [7].…”

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“…It has been shown by extensive Green's function calculations for a number of van der Waals and hydrogen bonded systems that the level structure turns out such that this reduction in energy is sufficient to render inner-valence hole states unstable towards decay into doubly charged cations with distributed vacancies [4 -6]. The physical picture behind the IC decay of these states is fairly clear [5,10]: The initial inner-valence hole is filled by an outer-valence electron from the same site. The energy released by this transition is consumed to eject another outer-valence electron from a neighboring site.…”

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“…Here, the photon energy is sufficient for photo double ionization of a single site within the cluster. The energy for this process has been calculated as 60.9 eV for Ne 2 and slightly lower for Ne 3 [5]. For atomic Ne, 62.53 eV were found experimentally [15].…”

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“…The broadening of the ICD structure due to the underlying doubly charged states can be estimated as 0.75 eV for the central atom in a Ne 13 configuration [17,18]. For the decay of surface atoms, a lesser number of different states is important; on the other hand, here the ICD line might be broadened due to the effect of the subsequent Coulomb explosion of the system [5]. Additional broadening of the observed electron lines in our experiment, as compared to the calculation, can be expected, since our cluster beam contains a distribution of different cluster sizes and since we cannot distinguish ICD electrons emitted from different sites within the cluster.…”

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Experimental Evidence for Interatomic Coulombic Decay in Ne Clusters

et al. 2003

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Electron spectra of photoexcited Ne clusters are shown to display a signal at low kinetic energies that is neither present in the Ne monomer nor at photon energies below the inner-valence 2s threshold. These findings are strong evidence for the existence of interatomic Coulombic decays (ICD), a mechanism that was recently predicted theoretically [Phys. Rev. Lett. 79, 4778 (1997)]. In ICD, an inner-valence hole state in a weakly bonded system can undergo ultrafast relaxation due to energy transfer to a neighboring atom, followed by electron emission from this neighboring site. DOI: 10.1103/PhysRevLett.90.203401 PACS numbers: 36.40.Mr, 33.80.Eh, 34.30.+h, 82.33.Fg The nonradiative decay of a core hole vacancy in an excited atom by electron emission is a well known process in spectroscopy, commonly denoted as Auger decay. Traditionally, it is assumed that in extended aggregates -molecules or bulk matter-electrons only at the excited site actively take part in the decay and that the environment of the initially excited atom only modifies the Auger energy spectrum via its influence on the energy levels [1][2][3]. In contrast to that, for weakly bound aggregates, such as van der Waals clusters and hydrogen bonded systems, a radiationless decay mechanism has been predicted, which is possible only by electron emission from neighboring sites of the vacancy [4][5][6]. The final states populated in this so-called ''interatomic Coulombic decay'' (ICD) thus have two positive charges distributed at two different atoms of the system [7]. This lowers their total energy by shielding the Coulomb repulsion of the final state holes. For a lot of systems, it is just this shift in final state energy which makes the decay energetically possible. Where present, ICD should be an ultrafast relaxation pathway, which proceeds on time scales of 1-100 fs. It is therefore expected that it dominates over competing channels, like radiative decay or relaxation involving the nuclear dynamics.Although recently an indirect indication of the relevance of interatomic transitions in the core vacancy decay of molecules has been found [8], an experimental verification of the effect is missing. The major reason for this is probably the low kinetic energy of the electrons emitted by ICD, which is typically a few eV. The unambiguous identification of these electrons would be the only distinct proof for the process. However, the region close to zero kinetic energy in the electron spectrum of a bulk material exposed to vacuum ultraviolet radiation is dominated by inelastically scattered photoelectrons from the valence band. The same is true for clusters, but due to the limited spatial dimensions of the system short range effects like ICD make a relatively higher contribution to the signal close to zero kinetic energy.In this Letter we present direct experimental evidence for ICD in the photoexcited electron spectra of small Ne clusters.In the following, we first introduce the ICD mechanism in some detail. Excited electronic states can decay in two ways, ...

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Experimental Evidence for Interatomic Coulombic Decay in Ne Clusters

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“…Extensive theoretical work has been carried out on ICD in neon clusters [5][6][7][8][9][10] and many other species [1,11]. For the case of ICD after 2s photoionization in neon dimers, the decay rate is proportional to jV L2p;R2p;L2s;k ÿ V L2p;R2p;k;L2s j 2 , where the two electron-electron Coulomb matrix elements (2) are denoted as ''direct'' and ''exchange'' contribution, respectively [6,12].…”

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Experimental Separation of Virtual Photon Exchange and Electron Transfer in Interatomic Coulombic Decay of Neon Dimers

et al. 2007

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Access and use of this website and the material on it are subject to the Terms and Conditions set forth at Vous avez des questions? Nous pouvons vous aider. Pour communiquer directement avec un auteur, consultez la première page de la revue dans laquelle son article a été publié afin de trouver ses coordonnées. Si vous n'arrivez pas à les repérer, communiquez avec nous à PublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca. Experimental separation of virtual photon exchange and electron transfer in interatomic Coulombic decay of neon dimers Questions? Contact the NRC Publications Archive team atPublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca. If you wish to email the authors directly, please see the first page of the publication for their contact information. NRC Publications Archive Archives des publications du CNRCThis publication could be one of several versions: author's original, accepted manuscript or the publisher's version. / La version de cette publication peut être l'une des suivantes : la version prépublication de l'auteur, la version acceptée du manuscrit ou la version de l'éditeur. For the publisher's version, please access the DOI link below./ Pour consulter la version de l'éditeur, utilisez le lien DOI ci-dessous.http://doi.org/10.1103/PhysRevLett.99.153401Physical Review Letters, 99, pp. 153401-1-153401-4, 2007-10-12 Experimental Separation of Virtual Photon Exchange and Electron Transfer in InteratomicCoulombic Decay of Neon Dimers We investigate the interatomic Coulombic decay (ICD) of neon dimers following photoionization with simultaneous excitation of the ionized atom (shakeup) in a multiparticle coincidence experiment. We find that, depending on the parity of the excited state, which determines whether ICD takes place via virtual dipole photon emission or overlap of the wave functions, the decay happens at different internuclear distances, illustrating that nuclear dynamics heavily influence the electronic decay in the neon dimer.

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Generation of Highly Damaging H₂O⁺ Radicals by Inner Valence Shell Ionization of Water

2010

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[a] Water molecules surround all biological matter and have a crucial role as the matrix of life. Owing to the close proximity of water molecules to all biological systems, it is important to understand the response of water to ionizing sources, since the emitted electrons and open-shell fragments play a major role in various damaging mechanisms of biomolecules. Very recent experiments have investigated the inner valence ionization of water in the water dimer [1] and in larger water clusters, [2] and have found that the system decays emitting electrons of low energy and radical cations H 2 O + . Low-energy electrons can effectively interact and induce breakage of biomolecules. The water radical cation is also capable of great damage. [3,4] It is a strong acid and will immediately transfer a proton to any nearby group with proton-accepting capability. The proton transfer results in OHC, which is extremely reactive itself. In nature and experimentally the inner valence ionization can be accomplished by interaction with light. Other preparations are also conceivable, for example, an inner-valence ionized state can be the result of a cascade of processes, such as Auger decay, started by ionization or excitation of a core electron by an energetic particle or photon. The process by which an inner-valence ionized state decays by emission of an electron is called intermolecular Coulombic decay (ICD). ICD is an electronic deexcitation process that was first theoretically predicted for hydrogen-bonded systems [5,6] and van der Waals clusters of noble gas atoms. [7] Later, experimental evidence of ICD in van der Waals clusters was reported, [8,9] and more recently, evidence of ICD in water has been reported as well.[1, 2, 10] ICD can take place if the inner valence ionized state is energetically above the double-ionization threshold of the system. This is usually not the case for isolated atoms or small molecules. However, for aggregates, the double ionization threshold can fall below the inner valence ionization energy, opening the possibility for ICD to occur. The process can be described as a relaxation of the ionized atom or molecule, in which an outer valence electron fills the inner valence hole. The energy released is transferred to a neighboring species, from which a second outer valence electron is expelled. In the case of the water dimer, the double ionization threshold is about 3 to 4 eV below the inner valence ionization energy, and therefore ICD follows an inner valence ionization process. [6] In the experiments on the water dimer of ref.[1], the ICD process is triggered by ionization from an inner valence shell of one of the water molecules. The two emitted electrons (direct photo-electron and ICD electron) and the cationic fragments resulting from the Coulomb explosion of the dimer are then measured in coincidence, determining their directions, and the charges and masses of the fragments. Such experiments clearly show that ICD results in two H 2 O + fragments, which immediately separate in a Coulomb explo...

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Interatomic Coulombic Decay in van der Waals Clusters and Impact of Nuclear Motion

Cited by 167 publications

References 21 publications

Experimental Evidence for Interatomic Coulombic Decay in Ne Clusters

Experimental Evidence for Interatomic Coulombic Decay in Ne Clusters

Experimental Separation of Virtual Photon Exchange and Electron Transfer in Interatomic Coulombic Decay of Neon Dimers

Generation of Highly Damaging H₂O⁺ Radicals by Inner Valence Shell Ionization of Water

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Interatomic Coulombic Decay in van der Waals Clusters and Impact of Nuclear Motion

Cited by 167 publications

References 21 publications

Experimental Evidence for Interatomic Coulombic Decay in Ne Clusters

Experimental Evidence for Interatomic Coulombic Decay in Ne Clusters

Experimental Separation of Virtual Photon Exchange and Electron Transfer in Interatomic Coulombic Decay of Neon Dimers

Generation of Highly Damaging H2O+ Radicals by Inner Valence Shell Ionization of Water

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Generation of Highly Damaging H₂O⁺ Radicals by Inner Valence Shell Ionization of Water