Ludger Inhester

Ludger Inhester
Deutsches Elektronen-Synchrotron · Center for Free-Electron Laser Science

Dipl. Phys. Dr. rer. nat.

About

58
Publications
6,332
Reads
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615
Citations
Additional affiliations
April 2020 - present
Center for Free-Electron Laser Science
Position
  • Senior Researcher
October 2019 - March 2020
SimCog Technologies GmbH
Position
  • Analyst
October 2014 - September 2019
Center for Free-Electron Laser Science
Position
  • PostDoc Position
Education
August 2009 - August 2013
October 2005 - May 2009
October 2003 - October 2005

Publications

Publications (58)
Article
The “hole” story of water ionization The direct observation of the cationic hole H 2 O ⁺ that is formed in liquid water after ionization has been a long-standing experimental challenge. Previous attempts using optical and ultraviolet techniques have failed to reveal its key spectroscopic signature during ultrafast transformation into a OH radical....
Article
Full-text available
Coulomb explosion imaging is a promising experimental tool to study individual molecules. In this work simulation data for the x-ray induced Coulomb explosion of 2-iodopyridine is analyzed and the involved fragmentation dynamics are described. It is found that particular final ion momenta show correlations that reflect a collision of two atoms duri...
Article
Full-text available
The ultrafast structural dynamics of water following inner-shell ionization is a crucial issue in high-energy radiation chemistry. We have exposed isolated water molecules to a short x-ray pulse from a free-electron laser and detected momenta of all produced ions in coincidence. By combining experimental results and theoretical modeling, we can ima...
Article
Full-text available
X-ray free-electron lasers enable the investigation of the structure and dynamics of diverse systems, including atoms, molecules, nanocrystals and single bioparticles, under extreme conditions. Many imaging applications that target biological systems and complex materials use hard X-ray pulses with extremely high peak intensities (exceeding 10 20 w...
Article
The advent of ultrashort soft x-ray pulse sources permits the use of established gas phase spectroscopy methods to investigate ultrafast photochemistry in isolated molecules with element and site specificity. In the present study, we simulate excited state wavepacket dynamics of a prototypical process, the ultrafast photodissociation of methyl iodi...
Article
Full-text available
Inner-shell photoelectron spectroscopy provides an element-specific probe of molecular structure, as core-electron binding energies are sensitive to the chemical environment. Short-wavelength femtosecond light sources, such as Free-Electron Lasers (FELs), even enable time-resolved site-specific investigations of molecular photochemistry. Here, we s...
Article
Full-text available
Following structural dynamics in real time is a fundamental goal towards a better understanding of chemical reactions. Recording snapshots of individual molecules with ultrashort exposure times is a key ingredient towards this goal, as atoms move on femtosecond (10−15 s) timescales. For condensed-phase samples, ultrafast, atomically resolved struct...
Article
Full-text available
The inclusion of nuclear quantum effects (NQEs) in molecular dynamics simulations is one of the major obstacles for an accurate modeling of molecular scattering processes involving more than a couple of atoms. An efficient method to incorporate these effects is ring polymer molecular dynamics (RPMD). Here we extend the scope of our recently develop...
Article
The dynamics of molecules exposed to intense x-ray radiation involve a large number of multiply ionized and highly excited electronic configurations. To model these dynamics a reliable and efficient electronic structure model is imperative. Employing the Hartree-Fock-Slater electronic structure model in combination with the maximum overlap method,...
Article
The interaction of intense femtosecond x-ray pulses with molecules sensitively depends on the interplay between multiple photoabsorptions, Auger decay, charge rearrangement, and nuclear motion. Here, we report on a combined experimental and theoretical study of the ionization and fragmentation of iodomethane (CH3I) by ultraintense (∼1019 W/cm2) x-r...
Article
Full-text available
Short-wavelength free-electron lasers with their ultrashort pulses at high intensities have originated new approaches for tracking molecular dynamics from the vista of specific sites. X-ray pump X-ray probe schemes even allow to address individual atomic constituents with a ‘trigger’-event that preludes the subsequent molecular dynamics while being...
Article
Full-text available
Investigating the early dynamics of chemical systems following ionization is essential for our understanding of radiation damage. However,experimental as well as theoretical investigations are very challenging due to the complex nature of these processes. Time-resolved x-ray absorption spectroscopy on a femtosecond timescale, in combination with ap...
Article
Full-text available
Molecules can sequentially absorb multiple photons when irradiated by an intense X-ray pulse from a free-electron laser. If the time delay between two photoabsorption events can be determined, this enables pump-probe experiments with a single X-ray pulse, where the absorption of the first photon induces electronic and nuclear dynamics that are prob...
Preprint
Full-text available
Short-wavelength free-electron lasers with their ultrashort pulses at high intensities have originated new approaches for tracking molecular dynamics from the vista of specific sites. X-ray pump X-ray probe schemes even allow to address individual atomic constituents with a 'trigger'-event that preludes the subsequent molecular dynamics while being...
Article
Full-text available
Attosecond pulses can be used to generate coherent superpositions of cationic electronic states in molecules through photoionisation. These can drive coherent electronic dynamics, which may decay within a few femtoseconds due to nuclear motion. In this work, we study the impact of the photoelectron on decoherence in the valence electron system of m...
Article
Full-text available
To date, alternating co-polymers based on electron-rich and electron-poor units are the most attractive materials to control functionality of organic semiconductor layers in which ultrafast excited-state processes play a key role. We present a computational study of the photoinduced excited-state dynamics of the 4-(2-thienyl)-2,1,3-benzothiadiazole...
Conference Paper
Full-text available
Synopsis The ultra-intense and ultra-short x-ray pulses provided by X-ray Free-Electron Lasers (XFELs) sequentially ionize molecular samples many times. In this context, we have recently discovered that under intense x-ray radiation the total charge of a molecule is enhanced compared to the sum of charges of its constituent isolated atoms[2, 3]. We...
Preprint
Full-text available
The advent of ultrashort soft x-ray pulse sources permits the use of established gas phase spectroscopy methods to investigate ultrafast photochemistry in isolated molecules with element and site specificity. In the present study, we simulate excited state wavepacket dynamics of a prototypical process, the ultrafast photodissociation of methyl iodi...
Data
Double core ionization of N2 via two sub-femtosecond x-ray pulses. The figure shows the intensity of the second photoelectron as a function of emission angle for selected delay times t and fixed emission angle of the first photoelectron and averaged over the orientation of the molecule with respect to the polarization axis. T is the core-hole osci...
Article
Full-text available
We propose an imaging technique to follow core-hole wave-packet oscillations in the nitrogen molecule. In this scheme, an attosecond x-ray pulse core-ionizes the nitrogen molecule and a subsequent attosecond x-ray pulse probes the evolution of the electron dynamics. We can image the oscillation of the core-hole between the two atomic sites by measu...
Article
Full-text available
Determination of the electronic structure of mass-selected transient molecular ions which can be considered as building blocks of biomolecules.
Article
Full-text available
Theoretical and experimental methodologies that can characterize electronic and nuclear dynamics, and the coupling between the two, are needed to understand photoinduced charge transfer in molecular building blocks used in organic photovoltaics. Ongoing developments in ultrafast pump-probe techniques such as time-resolved X-ray absorption spectrosc...
Conference Paper
Full-text available
Synopsis (X-ray) free-electron lasers are employed to site specifically interrogate atomic fragments during ultra-fast photolysis of chiral molecules via time-resolved photoelectron circular dichroism.
Preprint
Full-text available
We propose an imaging technique to follow core-hole wave-packet oscillations in the nitrogen molecule. In this scheme, an attosecond x-ray pulse core-ionizes the nitrogen molecule and a subsequent attosecond x-ray pulse probes the evolution of the electron dynamics. We can image the oscillation of the core-hole between the two atomic sites by measu...
Article
Full-text available
It was recently discovered that molecular ionization at high x-ray intensity is enhanced, in comparison with that of isolated atoms, through a phenomenon called CREXIM (charge-rearrangement-enhanced x-ray ionization of molecules). X-ray absorption selectively ionizes heavy atoms within molecules, triggering electron transfer from neighboring atoms...
Preprint
Full-text available
It was recently discovered that molecular ionization at high x-ray intensity is enhanced, in comparison with that of isolated atoms, through a phenomenon called CREXIM (charge-rearrangement-enhanced x-ray ionization of molecules). X-ray absorption selectively ionizes heavy atoms within molecules, triggering electron transfer from neighboring atoms...
Preprint
Full-text available
Highly intense, sub-picosecond terahertz (THz) pulses can be used to induce ultrafast temperature jumps (T-jumps) in liquid water. A supercritical state of gas-like water with liquid density is established, and the accompanying structural changes are expected to give rise to time-dependent chemical shifts. We investigate the possibility of using ex...
Conference Paper
Full-text available
We simulated the multi-photon multi-ionization dynamics of an iodomethane molecule, CH 3 I, exposed to ultraintense and ultrashort x-ray pulses. The strong ionization causes electronic charge rearrangement in the molecule that leads to an enhanced total charge.
Article
We present a combined experimental and theoretical study of the Auger-emission spectrum following double core ionization and excitation of gas-phase water molecules with hard-x-ray synchrotron radiation above the O K−2 threshold. We observe an indication of ultrafast proton motion occurring within the 1.5 fs lifetime of the double-core-hole (DCH) s...
Article
With the highly intense x-ray light generated by x-ray free-electron lasers (XFELs), molecular samples can be ionized many times in a single pulse. Here we report on a computational study of molecular spectroscopy at the high x-ray intensity provided by XFELs. Calculated photoelectron, Auger electron, and x-ray fluorescence spectra are presented fo...
Article
In many cases fragmentation of molecules upon inner-shell ionization is very unspecific with respect to the initially localized ionization site. Often this finding is interpreted in terms of an equilibration of internal energy into vibrational degrees of freedom after Auger decay. Here we investigate the x-ray photofragmentation of ethyl trifluoroa...
Article
Full-text available
Ultrafast proton migration and isomerization are key processes for acetylene and its ions. However, the mechanism for ultrafast isomerization of acetylene [HCCH]²⁺ to vinylidene [H2CC]²⁺ dication remains nebulous. Theoretical studies show a large potential barrier ( > 2 eV) for isomerization on low-lying dicationic states, implying picosecond or lo...
Article
Hydration shells around ions are crucial for many fundamental biological and chemical processes. Their local physico-chemical properties are quite different from bulk water, and hard to probe experimentally. We address this problem by combining soft X-ray spectroscopy using a liquid jet and molecular dynamics (MD) simulations together with ab initi...
Article
There has been a considerable debate on the existence of a low-barrier hydrogen bond (LBHB) in the photoactive yellow protein (PYP). The debate was initially triggered by the neutron diffraction study of Yamaguchi et al. (Proc.Natl.Acad.Sci.,USA, 2009,106,440-444) who suggested a model, in which a neutral ARG52 residue triggers the formation of the...
Article
Full-text available
We present a theoretical investigation of x-ray multiphoton ionization dynamics of polyatomic molecules, based on the rate equation model and molecular electronic structure calculations. An efficient numerical procedure is developed to calculate photoionization cross sections, Auger rates, and fluorescence rates for all possible electronic multiple...
Preprint
Full-text available
Experimental evidence has pointed toward the existence of ultrafast proton migration and isomerization as a key process for acetylene and its ions, however the actual mechanism for ultrafast isomerization of the acetylene [HCCH]2+ to vinylidene [H2CC]2+ dication remains nebulous. Theoretical studies show a high potential barrier of over 2 eV [J. Ch...
Article
Full-text available
We present the implementation of an electronic-structure approach dedicated to ionization dynamics of molecules interacting with x-ray free-electron laser (XFEL) pulses. In our scheme, molecular orbitals for molecular core-hole states are represented by linear combination of numerical atomic orbitals that are solutions of corresponding atomic core-...
Thesis
Full-text available
X-ray free electron lasers allow to create and probe double core holes in molecules via successive ionization in considerable amount. The properties of these double core ionized states are in particular relevant for the radiation damage in X-ray coherent diffractive imaging (CDI) experiments with single molecules. In this thesis the Auger decay of...
Article
Because of the high intensity, X-ray free electron lasers allow one to create and probe double core ionized states in molecules. The decay of these multiple core ionized states crucially determines the evolution of radiation damage in single molecule diffractive imaging experiments. Here we have studied the Auger decay in hydrides of first row elem...
Article
Full-text available
The high intensity of free electron lasers opens up the possibility to perform single-shot molecule scattering experiments. However, even for small molecules, radiation damage induced by absorption of high intense x-ray radiation is not yet fully understood. One of the striking effects which occurs under intense x-ray illumination is the creation o...
Article
The high intensity of new x-ray sources such as Free Electron Lasers (FEL) offers the possibility to do single-shot molecule diffraction experiments. Even for small molecules, the dynamics induced by the radiation damage in such experiments are not yet fully understood. In particular, double core-ionized molecules are expected to be created in cons...
Article
Full-text available
The joint probability distribution in the full counting statistics (FCS) for noninteracting electrons is discussed for an arbitrary number of initially separate subsystems which are connected at t=0 and separated at a later time. A simple method to obtain the leading order long time contribution to the logarithm of the characteristic function is pr...

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Projects

Projects (2)
Project
The 2022 PULSE/CFEL Ultrafast X-ray Summer School will take place at the SLAC National Accelerator Laboratory this summer (June 20-23). The school will feature lectures from experts in ultrafast X-ray science. In addition, we are planning activities to further engage students including laboratory sessions aimed at teaching students how to analyze datasets recorded at XFEL facilities. We are currently planning for an in-person meeting at SLAC National Accelerator Laboratory, Menlo Park, CA, USA. However, it is not clear that this will be possible given the status of the COVID-19 pandemic. Registration is open till June 01. Information can be found on the website https://web.stanford.edu/group/pulse_institute/uxss2022/ along with the full speaker list, and a full agenda. We will try to offer travel stipends to as many students as possible. Ludger Inhester(UXSS 2022 Co-Chair) JamesCryan(UXSS 2022 Chair)