Thomas Pfeifer
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View article: Visualizing the strong field–induced molecular breakup of C <sub>60</sub> via x-ray diffraction
Visualizing the strong field–induced molecular breakup of C <sub>60</sub> via x-ray diffraction Open
Laser-driven dynamics in polyatomic molecules poses a complex many-body problem. Understanding intense light-matter interaction is crucial for steering intramolecular quantum dynamical processes. Here, we record time-resolved x-ray diffrac…
View article: Emergence of pseudoresonance in high-intensity resonant inelastic x-ray scattering
Emergence of pseudoresonance in high-intensity resonant inelastic x-ray scattering Open
We report resonant inelastic x-ray scattering (RIXS) spectra of neon atoms interacting with intense x-ray pulses generated using an x-ray free-electron laser (XFEL). We find that an unexpected peak emerges near the K α line of Ne, whic…
View article: Optical transitions near the elusive <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mn>5</mml:mn> <mml:mi>s</mml:mi> <mml:mtext>−</mml:mtext> <mml:mn>4</mml:mn> <mml:mi>f</mml:mi> </mml:mrow> </mml:math> level crossing in highly charged osmium with sensitivity to physics beyond the standard model
Optical transitions near the elusive level crossing in highly charged osmium with sensitivity to physics beyond the standard model Open
Optical transitions in highly charged ions can be very sensitive to hypothetical beyond-the-standard-model phenomena. Those near the degeneracy due to the 5 s − 4 f level crossing are especially promising. We present measurements of …
View article: Two-dimensional spectral interferometry in the extreme-ultraviolet enabled by computational phase-stabilization
Two-dimensional spectral interferometry in the extreme-ultraviolet enabled by computational phase-stabilization Open
In this paper, the concept of spectral interferometry is transferred to the extreme ultraviolet (XUV) by a two-fold approach. On the one hand, in addition to the frequency-resolved spectrogram, a spatial dimension is added to the analysis …
View article: Entanglement in photoionisation reveals the effect of ionic coupling in attosecond time delays
Entanglement in photoionisation reveals the effect of ionic coupling in attosecond time delays Open
View article: Single-shot sorting of Mössbauer time-domain data at X-ray free electron lasers
Single-shot sorting of Mössbauer time-domain data at X-ray free electron lasers Open
Mössbauer spectroscopy is widely used to study structure and dynamics of matter with remarkably high energy resolution, provided by the narrow nuclear resonance line widths. However, the narrow width implies low count rates, such that expe…
View article: Glow discharge induced reactions in mixtures of ozone and chlorodifluoromethane with atmospheric gases
Glow discharge induced reactions in mixtures of ozone and chlorodifluoromethane with atmospheric gases Open
The influence of extraterrestrial particles like cosmic radiation (CR) on the chemistry and ozone density in the Earth stratosphere is not well investigated and normally neglected in stratospheric chemistry models. Here we present the comm…
View article: Multiply differential study of detachment with simultaneous target excitation in anion-atom collisions
Multiply differential study of detachment with simultaneous target excitation in anion-atom collisions Open
We have measured momenta of electrons and recoil ions in triple coincidence with neutralized projectiles for slow collisions between various anions and target atoms. From the data we extracted triple differential momentum and angular distr…
View article: Study of the elusive $5s-4f$ level crossing in highly charged osmium with optical transitions suitable for physics beyond the Standard Model searches
Study of the elusive $5s-4f$ level crossing in highly charged osmium with optical transitions suitable for physics beyond the Standard Model searches Open
Optical transitions of highly charged ions can be very sensitive to hypothetical beyond-the-Standard-Model phenomena. Those near the $5s-4f$ level crossing, where the $5s$ and $4f$ are degenerate are especially promising. We present predic…
View article: Dichography: Two-frame Ultrafast Imaging from a Single Diffraction Pattern
Dichography: Two-frame Ultrafast Imaging from a Single Diffraction Pattern Open
X-ray free-electron lasers can nowadays deliver pairs of ultrabright, ultrashort light pulses with controllable delays at different photon energies. When combined with diffraction experiments, the interaction of these pulses with a sample …
View article: Super-resolution stimulated X-ray Raman spectroscopy
Super-resolution stimulated X-ray Raman spectroscopy Open
Propagation of intense X-ray pulses through dense media has led to the observation of phenomena such as atomic X-ray lasing1,2, self-induced transparency3 and stimulated X-ray Raman scattering (SXRS)4. SXRS…
View article: Comprehensive Laboratory Benchmark of K-shell Dielectronic Satellites of Fe <scp>xxv</scp>–<scp>xxi</scp> Ions
Comprehensive Laboratory Benchmark of K-shell Dielectronic Satellites of Fe <span>xxv</span>–<span>xxi</span> Ions Open
We report on comprehensive laboratory studies of the K-shell dielectronic recombination resonances of Fe xxv – xxi ions that prominently contribute to the hard X-ray spectrum of hot astrophysical plasmas. By scanning a monoenergetic electr…
View article: Phase evolution of strong-field ionization
Phase evolution of strong-field ionization Open
We investigate the time-dependent evolution of the dipole phase shift induced by strong-field ionization (SFI) using attosecond transient absorption spectroscopy (ATAS) for time delays where the pump-probe pulses overlap. We study measured…
View article: Bringing weak transitions to light
Bringing weak transitions to light Open
Weak transitions between quantum states are of fundamental importance for a broad range of phenomena from analytical biochemistry to precision physics, but generally challenge experimental detection. Due to their small cross sections scali…
View article: Extracting RABBITT-like phase information from time-dependent transient absorption spectra
Extracting RABBITT-like phase information from time-dependent transient absorption spectra Open
We explore how the spectral phase of attosecond pulse trains influences the optical cross section in transient absorption (TA) spectroscopy. The interaction of extreme ultraviolet (XUV) and time-delayed near-infrared (NIR) fields with an a…
View article: Experimental triple-differential cross sections for electron-impact ionization of 1-methyl-5-nitroimidazole at 97-eV impact energy
Experimental triple-differential cross sections for electron-impact ionization of 1-methyl-5-nitroimidazole at 97-eV impact energy Open
We present the triple-differential cross sections (TDCSs) for electron-impact single ionization of a potential radiosensitizer molecule, 1-methyl,5-nitroimidazole (C4H5N3O2), at an impact energy of 97 eV. The experiment was done using a mo…
View article: Comprehensive Laboratory Benchmark of K-shell Dielectronic Satellites of Fe XXV-XXI Ions
Comprehensive Laboratory Benchmark of K-shell Dielectronic Satellites of Fe XXV-XXI Ions Open
We report on comprehensive laboratory studies of the K-shell dielectronic recombination (DR) resonances of Fe XXV - XXI ions that prominently contribute to the hard X-ray spectrum of hot astrophysical plasmas. By scanning a monoenergetic e…
View article: Enhanced intermolecular coulombic decay due to sulfur heteroatoms in thiophene dimer
Enhanced intermolecular coulombic decay due to sulfur heteroatoms in thiophene dimer Open
Intermolecular Coulombic decay (ICD) is an important relaxation process of excited atoms and molecules in an environment, producing low-energy electrons that may contribute to radiation damage. Despite its significance, the mechanisms infl…
View article: Bringing Weak Transitions to Light
Bringing Weak Transitions to Light Open
Weak transitions between quantum states are of fundamental importance for a broad range of phenomena from analytical biochemistry to precision physics, but generally challenge experimental detection. Due to their small cross sections scali…
View article: Resonant propagation of extreme-ultraviolet pulses through strongly driven high-density media
Resonant propagation of extreme-ultraviolet pulses through strongly driven high-density media Open
We show that by combining strong-field dressing and resonant propagation of XUV pulses, the transition of absorption lines from their natural Lorentzian profiles through Fano and complex multipeak shapes all the way back to broadened near-…
View article: A Complete Picture of Electron-Nuclear Coupling Dynamics in H₂⁺
A Complete Picture of Electron-Nuclear Coupling Dynamics in H₂⁺ Open
Chemical reactivity is fundamentally governed by the coupled dynamics of electrons and nuclei, which extend beyond the scope of the Born-Oppenheimer approximation. Directly resolving these coupled motions on their intrinsic timescales has …
View article: Role of intermediate resonances in attosecond photoelectron interferometry in neon
Role of intermediate resonances in attosecond photoelectron interferometry in neon Open
Attosecond photoelectron interferometry based on the combination of an attosecond pulse train and a synchronized infrared field is a fundamental technique for the temporal characterization of attosecond waveforms and for the investigation …
View article: Momentum imaging of electrons and recoil ions from anion–neutral interactions in a cryogenic ion storage ring
Momentum imaging of electrons and recoil ions from anion–neutral interactions in a cryogenic ion storage ring Open
We have momentum-analyzed electrons and recoil ions in triple coincidence with projectiles neutralized in 300-keV Si−+Ar collisions. The experiment was performed at a cryogenic ion storage ring with an in-ring reaction microscope. Differen…
View article: Redirection and Reshaping of Intense Extreme-Ultraviolet Radiation
Redirection and Reshaping of Intense Extreme-Ultraviolet Radiation Open
The goal to control short-wavelength radiation for the investigation and manipulation of ultrafast dynamics in quantum systems coevolves with the growing availability of extreme-ultraviolet (XUV) and x-ray sources from high-harmonic genera…
View article: Formation of singly ionized oxygen atoms from <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:math> driven by XUV pulses: A toolkit for the breakup of free-electron-laser-driven diatomics
Formation of singly ionized oxygen atoms from driven by XUV pulses: A toolkit for the breakup of free-electron-laser-driven diatomics Open
We formulate a general hybrid quantum-classical technique to describe the interaction of diatomic molecules with XUV pulses. We demonstrate the accuracy of our model in the context of the interaction of the O2 molecule with an XUV pulse wi…
View article: Electron impact single and double ionization and dissociation: revisiting CF<sub>4</sub> and CHF<sub>3</sub> with an improved experimental method
Electron impact single and double ionization and dissociation: revisiting CF<sub>4</sub> and CHF<sub>3</sub> with an improved experimental method Open
Accurate absolute ionization cross sections are obtained for all detected fragmentation channels. A previously undetected ion CHF 3 + was identified.
View article: Nanometric probing with a femtosecond, intra-cavity standing wave
Nanometric probing with a femtosecond, intra-cavity standing wave Open
Optical standing waves are intrinsically nanometric, spatially fixed interference-field patterns. At a commensurate scale, metallic nanotips serve as coherent, atomic-sized electron sources. Here, we explore the localized photofield emissi…
View article: Hanle Effect for Lifetime Determinations in the Soft X-Ray Regime
Hanle Effect for Lifetime Determinations in the Soft X-Ray Regime Open
By exciting a series of 1s2 S0
View article: Role of intermediate resonances in attosecond photoelectron interferometry in neon
Role of intermediate resonances in attosecond photoelectron interferometry in neon Open
Attosecond photoelectron interferometry based on the combination of an attosecond pulse train and a synchronized infrared field is a fundamental technique for the temporal characterization of attosecond waveforms and for the investigation …
View article: Electron-electron-ion triple-coincidence experiment of electron-initiated valence ionization of small water clusters
Electron-electron-ion triple-coincidence experiment of electron-initiated valence ionization of small water clusters Open
The ionization and fragmentation of small water clusters induced by electron impact (80 eV) is investigated. Using a multiparticle coincidence spectrometer (reaction microscope), all three charged final state particles—two outgoing electro…