Evidence for Chirped Auger-Electron Emission

Schütte, Bernd; Bauch, S.; Frühling, Ulrike; Wieland, Marek; Gensch, Michael; Plönjes, Elke; Gaumnitz, Thomas; Azima, Armin; Bönitz, M.; Drescher, Markus

doi:10.1103/physrevlett.108.253003

Cited by 41 publications

(53 citation statements)

References 29 publications

(53 reference statements)

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“…Tracing electron motion and correlation on their natural time scales has become possible within the last decade due to enormous experimental progress in light-pulse technology and detection methods [1][2][3][4]. These experimental advancements and associated new possibilities for elucidating quantum motion on an ultrafast timescale challenge theory.…”

Section: Introductionmentioning

confidence: 99%

Time-dependent generalized-active-space configuration-interaction approach to photoionization dynamics of atoms and molecules

2014

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We present a wave-function based method to solve the time-dependent many-electron Schrödinger equation (TDSE) with special emphasis on strong-field ionization phenomena. The theory builds on the configuration-interaction (CI) approach supplemented by the generalized-active-space (GAS) concept from quantum chemistry. The latter allows for a controllable reduction in the number of configurations in the CI expansion by imposing restrictions on the active orbital space. The method is similar to the recently formulated time-dependent restricted-active-space (TD-RAS) CI method [D. Hochstuhl, and M. Bonitz, Phys. Rev. A 86, 053424 (2012)]. We present details of our implementation and address convergence properties with respect to the active spaces and the associated account of electron correlation in both ground state and excitation scenarios. We apply the TD-GASCI theory to strong-field ionization of polar diatomic molecules and illustrate how the method allows us to uncover a strong correlation-induced shift of the preferred direction of emission of photoelectrons.

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Section: Introductionmentioning

confidence: 99%

Time-dependent generalized-active-space configuration-interaction approach to photoionization dynamics of atoms and molecules

2014

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“…Even though it is rarely stressed in literature, the mapping of decay time to photoelectron energy naturally occurs whenever a decay produces a secondary electron, which is significantly faster than the photoelectron [26,27]. The change of the kinetic energy of the emitted particles is known as "post collision interaction" (PCI) [28].…”

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Evolution of Interatomic Coulombic Decay in the Time Domain

et al. 2013

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During the last 15 years a novel decay mechanism of excited atoms has been discovered and investigated. This so called "Interatomic Coulombic Decay" (ICD) involves the chemical environment of the electronically excited atom: the excitation energy is transferred (in many cases over long distances) to a neighbor of the initially excited particle usually ionizing that neighbor. It turned out that ICD is a very common decay route in nature as it occurs across van-der-Waals and hydrogen bonds. The time evolution of ICD is predicted to be highly complex, as its efficiency strongly depends on the distance of the atoms involved and this distance typically changes during the decay. Here we present the first direct measurement of the temporal evolution of ICD using a novel experimental approach.In 1997 Cederbaum and coworkers realized that the presence of loosely bound atomic or molecular neighbors opens a new relaxation pathway to an electronically excited atom or molecule. In the decay mechanism they proposed -termed Intermolecular Coulombic Decay (ICD) -the excited particle relaxes efficiently by transferring its excitation energy to a neighboring atom or molecule [1]. As a consequence the atom or molecule receiving the energy emits an electron of low kinetic energy. The occurrence of ICD was proven in experiments in the mid 2000s by means of electron spectroscopy [2] and multi-coincidence techniques [3]. Since that time a wealth of experimental and theoretical studies have shown that ICD is a rather common decay path in nature, as it occurs almost everywhere in loosely bound matter. It has been proven to occur after a manifold of initial excitation schemes such as innervalence shell ionization, after Auger cascades [4,5], resonant excitation [6,7], shakeup ionization [8] and resonant Auger decay. ICD has also been observed in many systems as rare gas clusters [9], even on surfaces [10] and small water droplets [11,12]. The latter suggested that ICD might play a role in radiation damage of living tissue [13], as it creates low energy electrons, which are known to be genotoxic [14,15]. More recently that scenario was reversed as it was suggested to employ ICD in treatment of tagged malignant cells [16]. Apart from these potential applications the elementary process of ICD is under investigation, as the decay is predicted to have a highly complex temporal * Electronic address: jahnke@atom.uni-frankfurt.de behavior. The efficiency and thus the decay times of ICD depend strongly on the size of the system, i.e. the number of neighboring particles and the distance between them and the excited particle. However, even for most simple possible model systems consisting of only two atoms the temporal evolution of the decay is non-trivial and predicted theoretically to exhibit exciting physics [17]: as ICD happens on a timescale that is fast compared to relaxation via photon emission, but comparable to the typical times of nuclear motion in the system, the dynamics of the decay is complicated and so far only theoretically explored...

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“…For atomic Auger decay following innershell ionization, PCI is well understood [25,26]. Recently Schütte et al [27] have experimentally verified the time dependent picture we have just discussed, by showing that the energy exchange between photoelectron and Auger electron indeed depends on the Auger emission time delay. For atomic multiple ionization, such recapture of the photoelectron by PCI, leads to a shifted onset of the production of higher charge states, as e.g.…”

Section: Pacs Numbersmentioning

confidence: 51%

Interatomic-Coulombic-decay-induced recapture of photoelectrons in helium dimers

et al. 2014

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We investigate the onset of photoionization shakeup induced interatomic Coulombic decay (ICD) in He2 at the He + * (n = 2) threshold by detecting two He + ions in coincidence. We find this threshold to be shifted towards higher energies compared to the same threshold in the monomer. The shifted onset of ion pairs created by ICD is attributed to a recapture of the threshold photoelectron after the emission of the faster ICD electron. PACS numbers:Excited ions can get rid of their excess energy via the emission of a photon or an electron. If, however, the excited atom is spatially close to other atoms and the excitation energy is above the ionization threshold of this neighbor, the excess energy can also be transfered to the neighbor where it leads to emission of an electron. This energy transfer process is termed interatomic Coulombic decay (ICD). It was introduced by Cederbaum and coworkers in 1997 [1] and was demonstrated experimentally first for Neon clusters [2] and Neon dimers [3]. The related interatomic Auger transitions in solid matter have ofen been discussed, but broad valence bands, surface/bulk differences and significant electron energy-loss processes do typically preclude a clear assignment of this process for solids. Many studies have shown since then that ICD is a very general phenomenon occuring in van der Waals bound (see e.g. [2][3][4][5]) and hydrogen bound systems (see e.g. [6][7][8]). It can be induced by photoionization (see e.g. [2,3]), photoexcitation [9][10][11][12], Auger decay [13,14], ion impact [15][16][17], and electron impact [18] or as in the present case after shakeup [19]. The most extreme system for which ICD has been reported is the Helium dimer [20,21]. The neutral He dimer is very weakly bound (about 95 neV) and the internuclear distance extends to very large distances, with the mean * Electronic address: doerner@atom.uni-frankfurt.de distance of about 52Å. ICD in He 2 can occur when one of the Helium atoms is ionized and its remaining electron is shaken up to any excited state (He + * (n=2,3...)). In the next step, the He + * (n=2)He contracts and during that nuclear motion it undergoes ICD. The electron of the exited He + relaxes to the ground state and the energy is transfered to the neutral neighbor where the ICD electron is emitted. Finally, the two He + ions Coulomb explode back-to-back: He-He hν −→ He + * -He + e ph ICD − −− → He + + He + + e ph + e ICD Usually, ICD and the subsequent Coulomb explosion is discussed in a two step picture, where the decay is independent from the initial ionization/excitation process. In the present work, we show that close to the ionization/excitation threshold this two step approximation breaks down. Photoelectron and ICD electron interaction can lead to recapture of the photoelectron into a bound state of one of the two ions, which quenches the Coulomb explosion. A direct link between the ionization process and ICD has been discussed in two contexts in the literature so far. The first is the recoil effect, where it has been shown ex...

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Evidence for Chirped Auger-Electron Emission

Cited by 41 publications

References 29 publications

Time-dependent generalized-active-space configuration-interaction approach to photoionization dynamics of atoms and molecules

Time-dependent generalized-active-space configuration-interaction approach to photoionization dynamics of atoms and molecules

Evolution of Interatomic Coulombic Decay in the Time Domain

Interatomic-Coulombic-decay-induced recapture of photoelectrons in helium dimers

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