Ultrafast charge transfer and atomic orbital polarization

Deppe, Martin H.; Föhlisch, Alexander; Hennies, Franz; Nagasono, Mitsuru; Beye, Martin; Sánchez‐Portal, Daniel; Echenique, Pedro M.; Würth, W.

doi:10.1063/1.2781395

Cited by 17 publications

(12 citation statements)

References 31 publications

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“…Density functional theory (DFT) calculations, together with a recursive method to obtain the Green's function of the surface, showed to be a remarkably reliable method to analyze such processes (38,39). They predicted a peculiar dependence of the charge transfer times on the exciting light polarization that was experimentally confirmed (40). Besides the S/Ru (0001) system, Ar monolayers on Ru(0001) also have been theoretically studied (38), finding again values and trends for the charge-transfer times in good agreement with core-hole-clock experiments.…”

Section: Spin-selective Ultrafast Transfer Of Electronsmentioning

confidence: 89%

Time-dependent electron phenomena at surfaces

Muiño

Sánchez‐Portal

Silkin

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

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Femtosecond and subfemtosecond time scales typically rule electron dynamics at metal surfaces. Recent advance in experimental techniques permits now remarkable precision in the description of these processes. In particular, shorter time scales, smaller system sizes, and spin-dependent effects are current targets of interest. In this article, we use state-of-the-art theoretical methods to analyze these refined features of electron dynamics. We show that the screening of localized charges at metal surfaces is created locally in the attosecond time scale, while collective excitations transfer the perturbation to larger distances in longer time scales. We predict that the elastic width of the resonance in excited alkali adsorbates on ferromagnetic surfaces can depend on spin orientation in a counterintuitive way. Finally, we quantitatively evaluate the electron-electron and electron-phonon contributions to the electronic excited states widths in ultrathin metal layers. We conclude that confinement and spin effects are key factors in the behavior of electron dynamics at metal surfaces.lifetimes | spin effects | time-dependent phenomena C hemistry is driven by electrons. Chemical dynamics is often determined by electron dynamics, with electronically excited states frequently acting as necessary intermediate steps in chemical activity. The understanding and control of charge transfer times and electronic excitation survival times is thus a necessary step to understand, control, and design physical and chemical processes at surfaces.Dynamics of electronic excitations at metal surfaces has been widely investigated both experimentally (1-6) and theoretically (5, 7-13). As a consequence, deep understanding has been reached about the mechanisms ruling electron decay and electron charge transfer. However, recent advances in experimental tools are raising new challenges, many of them linked to shorter time scales, smaller system sizes, and/or spin effects. In this article, we present fresh results on these expanding topics, in an effort to blaze trails in electron dynamics research.At surfaces, electron excitation, charge exchange, and electron decay typically take place in the femtosecond (fs) and attosecond (as) time scales (1 as ¼ 10 −18 s, 1 fs ¼ 10 −15 s) (i.e., at times much faster than any nuclear motion). Advance in laser-based experimental techniques has carried research on this field to a new frontier, in which direct measurements of electron processes in this time scale are possible. Attosecond spectroscopy, for instance, is nowadays able to discern the individual elementary steps in photoemission from surfaces (i.e., excitation, transport, and emission) (14, 15). Access to experimental information in the attosecond scale is asking for new theoretical concepts. In particular, one of the relevant questions is how electronic excitations are created in time and how the environment reacts in such time scale. In the photocreation of localized holes in adsorbates at metallic surfaces, this question can be reformulated as...

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Section: Spin-selective Ultrafast Transfer Of Electronsmentioning

confidence: 89%

Time-dependent electron phenomena at surfaces

Muiño

Sánchez‐Portal

Silkin

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

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“…Analogous to the pump-probe technique, this method relies on an intrinsic time scale, based on the lifetime of excited core-hole states, and is therefore referred to as core-hole clock spectroscopy [90][91][92][93][94][95]. The working principle of this synchrotron-based soft x-ray core-hole clock spectroscopy method, is summarized in Fig.…”

Section: Core Hole Clock Techniquementioning

confidence: 99%

Charge transfer across the molecule/metal interface using the core hole clock technique

Wang

Chen

Wee

2008

Surface Science Reports

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“…In a second experiment [20], we have checked this theoretical prediction by measuring and evaluating the decay spectra obtained for two different polarization directions of the incoming soft X-ray radiation with respect to the substrate surface. From the resulting data points in Figure 14.9, one can see that excitation into the 3p orbital perpendicular to the surface (left side) leads to very different delocalization of the excited electron as compared to excitation into the orbitals parallel to the surface (right side).…”

Section: Attosecond Charge Transfer and The Effect Of Orbital Polarizmentioning

confidence: 99%

Electron Transfer Investigated by X‐Ray Spectroscopy

Würth

Föhlisch

2010

Dynamics at Solid State Surfaces and Interfaces

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Electron transfer at surfaces and interfaces plays an important role in many different processes such as catalytic, biophysical, electrochemical, and photoinduced reactions, molecular electronics, and solar energy conversion. Transfer can occur either resonantly or inelastically, involving more than one electron. Transfer processes occur typically on femtosecond and subfemtosecond timescales for systems where the available density of states is high such as metals. To study the fundamental aspects of the dynamics of electron transfer, it is convenient to create an electron wave packet by photoexcitation and follow its evolution by suitable probe techniques. X-rays are particularly well suited in this respect because they allow site-and element-specific localized excitations in complex systems, lead to direct excitation to a specific state, and can probe the subsequent evolution of this particular state.In this chapter, we will focus on two very different approaches using soft X-rays to investigate electron transfer, namely, high-resolution core hole spectroscopy at thirdgeneration synchrotron sources, the so-called core hole clock method [1-3], and stroboscopic pump-probe experiments using ultrashort X-ray pulses from free electron laser sources. The examples that are chosen to illustrate the potential of X-ray spectroscopy to study electron transfer are taken exclusively from our own recent work. Hence, this is by no means meant to be an extensive and representative review of the field. Core Hole Clock SpectroscopyThe term core hole clock spectroscopy reflects the fact that in this type of spectroscopy, the intrinsic lifetime of a core hole state is used as an internal reference against which competing relaxation processes are timed. Basically, the decay of a resonantly excited core hole state is studied spectroscopically (excellent reviews with many references can be found in the literature [4][5][6][7]). We will discuss here only the nonradiative decay channels, which for core hole states created by the absorption of soft X-rays represent the majority of decay channels.

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Ultrafast charge transfer and atomic orbital polarization

Cited by 17 publications

References 31 publications

Time-dependent electron phenomena at surfaces

Time-dependent electron phenomena at surfaces

Charge transfer across the molecule/metal interface using the core hole clock technique

Electron Transfer Investigated by X‐Ray Spectroscopy

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