Towards time resolved core level photoelectron spectroscopy with femtosecond x-ray free-electron lasers

Pietzsch, Annette; Föhlisch, Alexander; Beye, Martin; Deppe, Martin H.; Hennies, Franz; Nagasono, Mitsuru; Suljoti, Edlira; Würth, W.; Gahl, Cornelius; Döbrich, K. M.; Melnikov, A.V.

doi:10.1088/1367-2630/10/3/033004

Cited by 103 publications

(111 citation statements)

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“…Several methods are under development trying to combine high time resolution with high photon energies. [17][18][19] Currently, our ATR detection scheme applied to solid surfaces enables photon energies up to 140 eV and time-resolution in the attosecond regime.…”

Section: Introductionmentioning

confidence: 99%

A flexible apparatus for attosecond photoelectron spectroscopy of solids and surfaces

Magerl

Neppl

Cavalieri

et al. 2011

Review of Scientific Instruments

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We describe an apparatus for attosecond photoelectron spectroscopy of solids and surfaces, which combines the generation of isolated attosecond extreme-ultraviolet (XUV) laser pulses by high harmonic generation in gases with time-resolved photoelectron detection and surface science techniques in an ultrahigh vacuum environment. This versatile setup provides isolated attosecond pulses with photon energies of up to 140 eV and few-cycle near infrared pulses for studying ultrafast electron dynamics in a large variety of surfaces and interfaces. The samples can be prepared and characterized on an atomic scale in a dedicated flexible surface science end station. The extensive possibilities offered by this apparatus are demonstrated by applying attosecond XUV pulses with a central photon energy of ∼125 eV in an attosecond streaking experiment of a xenon multilayer grown on a Re(0001) substrate

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Section: Introductionmentioning

confidence: 99%

A flexible apparatus for attosecond photoelectron spectroscopy of solids and surfaces

Magerl

Neppl

Cavalieri

et al. 2011

Review of Scientific Instruments

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“…In the first period of user operation at FLASH, we started to investigate the possibilities for time-resolved corelevel photoemission spectroscopy and time-resolved X-ray emission spectroscopy. In collaboration with other groups, we have been able to perform first time-resolved core-level photoemission experiments on optically pumped surfaces [32,33] and solids [34]. Furthermore, we have been able to demonstrate the possibility to follow electronic structure changes in a semiconductor after optical excitation of electron-hole pairs using X-ray emission spectroscopy [35].…”

Section: Time-resolved Soft X-ray Spectroscopymentioning

confidence: 99%

“…In this study, we have monitored the line shape of the spin-orbit split W4f core levels excited with 118.5 eV photons from the third harmonic of FLASH as a function of the number of photons/pulse [33]. From the experimental results, it is obvious that we can observe strong space effects above a certain number of incoming photons that can also be modeled theoretically [33,36]. However, it is also clear that photoemission experiments can be performed with a free electron laser source such as FLASH in a regime of fluences where space charge effects can be avoided completely.…”

Section: Laser-assisted Photoemissionmentioning

confidence: 99%

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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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“…Here, the Coulomb repulsion between all the emitted electrons on a sample's surface sets a limit to the number of photons per X-ray pulse that can be used to reach a certain energy resolution [7][8][9] , and this number decreases with decreasing X-ray spot size and pulse duration. Peak brilliance is therefore not the main figure of merit for a highresolution photoemission set-up.…”

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confidence: 99%

Single bunch X-ray pulses on demand from a multi-bunch synchrotron radiation source

et al. 2014

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Synchrotron radiation facilities routinely operate in a multi-bunch regime, but applications relying on time-of-flight schemes require single bunch operation. Here we show that pulse picking by resonant excitation in a storage ring creates in addition to the multi-bunch operation a distinct and separable single bunch soft X-ray source. It has variable polarization, a photon flux of up to 10 7 -10 9 ph s À 1 /0.1%BW at purity values of 10 4 -10 2 and a repetition rate of 1.25 MHz. The quasi-resonant excitation of incoherent betatron oscillations of electrons allows horizontal pulse separation at variable (also circular) polarization accessible for both, regular 30 ps pulses and ultrashort pulses of 2-3 ps duration. Combined with a new generation of angularly resolving electron spectrometers this creates unique opportunities for time-resolved photoemission studies as confirmed by time-of-flight spectra. Our pulse picking scheme is particularly suited for surface physics at diffraction-limited light sources promising ultimate spectral resolution.

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Towards time resolved core level photoelectron spectroscopy with femtosecond x-ray free-electron lasers

Cited by 103 publications

References 50 publications

A flexible apparatus for attosecond photoelectron spectroscopy of solids and surfaces

A flexible apparatus for attosecond photoelectron spectroscopy of solids and surfaces

Electron Transfer Investigated by X‐Ray Spectroscopy

Single bunch X-ray pulses on demand from a multi-bunch synchrotron radiation source

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