Publications

@article{doi:10.1021/jacs.4c01543,

title = {Direct Observation of a Roaming Intermediate and Its Dynamics},

author = {Grite L. Abma and Michael A. Parkes and Weronika O. Razmus and Yu Zhang and Adam S. Wyatt and Emma Springate and Richard T. Chapman and Daniel A. Horke and Russell S. Minns},

doi = {10.1021/jacs.4c01543},

year  = {2024},

date = {2024-04-29},

urldate = {2024-04-29},

journal = {J. Am. Chem. Soc.},

volume = {146},

number = {18},

pages = {12595-12600},

keywords = {dynamics, experimental design, HHG, intramolecular interactions, Non-adiabatic dynamics, Photoelectron spectroscopy},

pubstate = {published},

tppubtype = {article}

}

@article{doi:10.1021/acs.jpclett.4c00768,

title = {Preparation of Tautomer-Pure Molecular Beams by Electrostatic Deflection},

author = {Grite L. Abma and Michael A. Parkes and Daniel A. Horke},

doi = {10.1021/acs.jpclett.4c00768},

year  = {2024},

date = {2024-04-24},

urldate = {2024-04-24},

journal = {J. Phys. Chem. Lett.},

volume = {15},

number = {17},

pages = {4587-4592},

keywords = {Control, electrostatic deflector, experimental design, Isomer-effects, photoelectron imaging, Photoelectron spectroscopy},

pubstate = {published},

tppubtype = {article}

}

@article{ROTH2024168820,

title = {New aerodynamic lens injector for single particle diffractive imaging},

author = {Nils Roth and Daniel A. Horke and Jannik L\"{u}bke and Amit K. Samanta and Armando D. Estillore and Lena Worbs and Nicolai Pohlman and Kartik Ayyer and Andrew Morgan and Holger Fleckenstein and Martin Domaracky and Benjamin Erk and Christopher Passow and Jonathan Correa and Oleksandr Yefanov and Anton Barty and Sa\v{s}a Bajt and Richard A. Kirian and Henry N. Chapman and Jochen K\"{u}pper},

url = {https://www.sciencedirect.com/science/article/pii/S0168900223008112},

doi = {https://doi.org/10.1016/j.nima.2023.168820},

issn = {0168-9002},

year  = {2024},

date = {2024-01-01},

urldate = {2024-01-01},

journal = {Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment},

volume = {1058},

pages = {168820},

abstract = {An aerodynamic lens injector was developed specifically for the needs of single-particle diffractive imaging experiments at free-electron lasers. Its design allows for quick changes of injector geometries and focusing properties in order to optimize injection for specific individual samples. Here, we present results of its first use at the FLASH free-electron-laser facility. Recorded diffraction patterns of polystyrene spheres are modeled using Mie scattering, which allowed for the characterization of the particle beam under diffractive-imaging conditions and yielded good agreement with particle-trajectory simulations. The complex refractive index of polystyrene at λ=4.5nm was determined as m=0.976−0.001i.},

keywords = {crystallography, diffractive imaging, experimental design, nanoparticles, Simulation, Single-particle imaging, XFEL},

pubstate = {published},

tppubtype = {article}

}

@article{molecules28135058,

title = {High-Throughput UV Photoionization and Fragmentation of Neutral Biomolecules as a Structural Fingerprint},

author = {Siwen Wang and Yerbolat Dauletyarov and Daniel A. Horke},

doi = {10.3390/molecules28135058},

issn = {1420-3049},

year  = {2023},

date = {2023-06-28},

urldate = {2023-06-28},

journal = {Molecules},

volume = {28},

number = {13},

pages = {5058},

abstract = {We present UV photofragmentation studies of the structural isomers paracetamol, 3-Pyridinepropionic acid (3-PPIA) and (R)-(-)-2-Phenylglycine. In particular, we utilized a new laser-based thermal desorption source in combination with femtosecond multiphoton ionization at 343 nm and 257 nm. The continuous nature of our molecule source, combined with the 50 kHz repetition rate of the laser, allowed us to perform these experiments at high throughput. In particular, we present detailed laser intensity dependence studies at both wavelengths, producing 2D mass spectra with highly differential information about the underlying fragmentation processes. We show that UV photofragmentation produces highly isomer-specific mass spectra, and assign all major fragmentation pathways observed. The intensity-dependence measurements, furthermore, allowed us to evaluate the appearance intensities for each fragmentation channel, which helped to distinguish competing from consecutive fragmentation pathways.},

keywords = {LBTD, photofragmentation},

pubstate = {published},

tppubtype = {article}

}

@article{dauletyarovVaporizationIntactNeutral2023,

title = {Vaporization of Intact Neutral Biomolecules Using Laser-Based Thermal Desorption},

author = {Yerbolat Dauletyarov and Siwen Wang and Daniel A. Horke},

url = {https://pubs.acs.org/doi/10.1021/jasms.3c00194},

doi = {10.1021/jasms.3c00194},

issn = {1044-0305, 1879-1123},

year  = {2023},

date = {2023-06-01},

urldate = {2023-06-01},

journal = {J. Am. Soc. Mass Spectrom.},

volume = {34},

pages = {1538},

abstract = {The production of a clean neutral molecular sample is a crucial step in many gas-phase spectroscopy and reaction dynamics experiments investigating neutral species. Unfortunately, conventional methods based on heating cannot be used with most nonvolatile biomolecules due to their thermal instability. In this paper, we demonstrate the application of laser-based thermal desorption (LBTD) to produce neutral molecular plumes of biomolecules such as dipeptides and lipids. Specifically, we report mass spectra of glycylglycine, glycyl-L-alanine, and cholesterol obtained using LBTD vaporization, followed by soft femtosecond multiphoton ionization (fs-MPI) at 400 nm. For all molecules, the signal from the intact precursor ion was observed, highlighting the softness and applicability of the LBTD and fs-MPI approach. In more detail, cholesterol underwent hardly any fragmentation. Both dipeptides fragmented significantly, although mostly through only a single channel, which we attribute to the fs-MPI process.},

keywords = {experimental design, LBTD, photofragmentation},

pubstate = {published},

tppubtype = {article}

}

@article{D3CP00328K,

title = {High-throughput UV-photofragmentation studies of thymine and guanine},

author = {Siwen Wang and Yerbolat Dauletyarov and Peter Kr\"{u}ger and Daniel A. Horke},

url = {http://dx.doi.org/10.1039/D3CP00328K},

doi = {10.1039/D3CP00328K},

year  = {2023},

date = {2023-04-15},

urldate = {2023-01-01},

journal = {Phys. Chem. Chem. Phys.},

volume = {25},

pages = {12322},

publisher = {The Royal Society of Chemistry},

abstract = {High-throughput photofragmentation studies of thymine and guanine were performed at 257 and 343 nm and for a wide range of ionisation laser intensities. Combining a continuous laser-based thermal desorption source with femtosecond multiphoton ionisation using a 50 kHz repetition rate laser allowed us to produce detailed 2D maps of fragmentation as a function of incident laser intensity. The fragmentation was distinctly soft, the parent ions being at least an order of magnitude more abundant than fragment ions. For thymine there was a single dominant fragmentation channel, which involves consecutive HNCO and CO losses. In contrast, for guanine there were several competing ones, the most probable channel corresponding to CH2N2 loss through opening of the pyrimidine ring. The dependence of parent ion abundance on the ionisation laser intensity showed that at 257 nm the ionisation of thymine is a 1 + 1 resonance enhanced process through its open-shell singlet state.},

keywords = {experimental design, LBTD, photofragmentation},

pubstate = {published},

tppubtype = {article}

}

@article{caballoDisentanglingMultiphotonIonization2023,

title = {Disentangling Multiphoton Ionization and Dissociation Channels in Molecular Oxygen Using Photoelectron\textendashPhotoion Coincidence Imaging},

author = {Ana Caballo and Anders J. T. M. Huits and David H. Parker and Daniel A. Horke},

url = {https://pubs.acs.org/doi/10.1021/acs.jpca.2c06707},

doi = {10.1021/acs.jpca.2c06707},

issn = {1089-5639, 1520-5215},

year  = {2023},

date = {2023-01-01},

urldate = {2023-01-01},

journal = {J. Phys. Chem. A},

volume = {127},

number = {1},

pages = {92--98},

abstract = {Multiphoton excitation of molecular oxygen in the 392-408 nm region is studied using a tunable femtosecond laser coupled with a double velocity map imaging photoelectron- photoion coincidence spectrometer. The laser intensity is held at $\leqsim$1 TW/cm2 to ensure excitation in the perturbative regime, where the possibility of resonance enhanced multiphoton ionization (REMPI) can be investigated. O2+ production is found to be resonance enhanced around 400 nm via three-photon excitation to the e$'$3$Delta$u(v = 0) state, similar to results from REMPI studies using nanosecond dye lasers. O+ production reaches 7% of the total ion yield around 405 nm due to two processes: autoionization following five-photon excitation of O2, producing O2+(X(v)) in a wide range of vibrational states followed by two- or three-photon dissociation, or six-photon excitation to a superexcited O2** state followed by neutral dissociation and subsequent ionization of the electronically excited O atom. Coincidence detection is shown to be crucial in identifying these competing pathways.},

keywords = {Coincidence Imaging, photoelectron imaging, Photoelectron spectroscopy, velocity-map imaging},

pubstate = {published},

tppubtype = {article}

}

@article{wangComparingPulsedContinuous2022,

title = {Comparing Pulsed and Continuous Laser-Induced Acoustic Desorption (LIAD) as Sources for Intact Biomolecules},

author = {Siwen Wang and Grite L. Abma and Peter Kr\"{u}ger and Andre Roij and Michiel Balster and Niek Janssen and Daniel A. Horke},

url = {https://link.springer.com/10.1140/epjd/s10053-022-00459-7},

doi = {10.1140/epjd/s10053-022-00459-7},

issn = {1434-6060, 1434-6079},

year  = {2022},

date = {2022-07-01},

urldate = {2022-07-01},

journal = {Eur. Phys. J. D},

volume = {76},

number = {7},

pages = {128},

abstract = {A major obstacle to the gas-phase study of larger (bio)molecular systems is the vaporisation step, that is, the introduction of intact sample molecules into the gas-phase. A promising approach is the use of laser-induced acoustic desorption (LIAD) sources, which have been demonstrated using both nanosecond pulsed and continuous desorption lasers. We directly compare here both approaches for the first time under otherwise identical conditions using adenine as a prototypical biological molecule, and study the produced molecular plumes using femtosecond multiphoton ionisation. We observe different desorption mechanisms at play for the two different desorption laser sources; however, we find no evidence in either case that the desorption process leads to fragmentation of the target molecule unless excessive desorption energy is applied. This makes LIAD a powerful approach for techniques that require high density and high purity samples in the gas-phase, such as ultrafast dynamics studies or diffraction experiments.},

keywords = {experimental design, LBTD, photofragmentation},

pubstate = {published},

tppubtype = {article}

}

@article{abmaSinglecolorIsomerresolvedSpectroscopy2022,

title = {Single-Color Isomer-Resolved Spectroscopy},

author = {Grite L. Abma and Dries Kleuskens and Siwen Wang and Michiel Balster and Andre Roij and Niek Janssen and Daniel A. Horke},

url = {https://doi.org/10.1021/acs.jpca.2c02277},

doi = {10.1021/acs.jpca.2c02277},

year  = {2022},

date = {2022-06-01},

urldate = {2022-06-01},

journal = {The Journal of Physical Chemistry A},

volume = {126},

pages = {3811\textendash3815},

abstract = {Structural isomers, such as conformers or tautomers, are

of significant importance across chemistry and biology, as they can have

different functionalities. In gas-phase experiments using molecular

beams, formation of many different isomers cannot be prevented, and

their presence significantly complicates the assignment of spectral lines.

Current isomer-resolved spectroscopic techniques heavily rely on

theoretical calculations or make use of elaborate double-resonance

schemes. We show here that isomer-resolved spectroscopy can also be

performed using a single tunable laser. In particular, we demonstrate

single-color isomer-resolved spectroscopy by utilizing electrostatic

deflection to spatially separate the isomers. We show that for 3-

aminophenol we can spatially separate the syn and anti conformers and

use these pure samples to perform high-resolution REMPI spectroscopy, making the assignment of transitions to a particular isomer trivial, without any additional a priori information. This approach allows one to add isomer specificity to any molecular-beam-based experiment.},

keywords = {Control, electrostatic deflector, experimental design, Isomer-effects},

pubstate = {published},

tppubtype = {article}

}

@article{PhysRevApplied.17.044044,

title = {Optical Funnel to Guide and Focus Virus Particles for X-Ray Diffractive Imaging},

author = {Salah Awel and Sebastian Lavin-Varela and Nils Roth and Daniel A. Horke and Andrei V. Rode and Richard A. Kirian and Jochen K\"{u}pper and Henry N. Chapman},

url = {https://link.aps.org/doi/10.1103/PhysRevApplied.17.044044},

doi = {10.1103/PhysRevApplied.17.044044},

year  = {2022},

date = {2022-04-01},

journal = {Phys. Rev. Applied},

volume = {17},

number = {4},

pages = {044044},

publisher = {American Physical Society},

keywords = {diffractive imaging, nanoparticles},

pubstate = {published},

tppubtype = {article}

}

@article{Zhuang:IUCrJ9:204,

title = {Unsupervised Learning Approaches to Characterizing Heterogeneous Samples Using X-ray Single-Particle Imaging},

author = {Yulong Zhuang and Salah Awel and Anton Barty and Richard Bean and Johan Bielecki and Martin Bergemann and Benedikt J. Daurer and Tomas Ekeberg and Armando D. Estillore and Hans Fangohr and Klaus Giewekemeyer and Mark S. Hunter and Mikhail Karnevskiy and Richard A. Kirian and Henry Kirkwood and Yoonhee Kim and Jayanath Koliyadu and Holger Lange and Romain Letrun and Jannik L\"{u}bke and Abhishek Mall and Thomas Michelat and Andrew J. Morgan and Nils Roth and Amit K. Samanta and Tokushi Sato and Zhou Shen and Marcin Sikorski and Florian Schulz and John C. H. Spence and Patrik Vagovic and Tamme Wollweber and Lena Worbs and P. Lourdu Xavier and Oleksandr Yefanov and Filipe R. N. C. Maia and Daniel A. Horke and Jochen K\"{u}pper and N. Duane Loh and Adrian P. Mancuso and Henry N. Chapman and Kartik Ayyer},

url = {https://scripts.iucr.org/cgi-bin/paper?S2052252521012707},

doi = {10.1107/S2052252521012707},

issn = {2052-2525},

year  = {2022},

date = {2022-03-01},

urldate = {2022-03-14},

journal = {IUCrJ},

volume = {9},

number = {2},

pages = {204--214},

abstract = {One of the outstanding analytical problems in X-ray single-particle imaging (SPI) is the classification of structural heterogeneity, which is especially difficult given the low signal-to-noise ratios of individual patterns and the fact that even identical objects can yield patterns that vary greatly when orientation is taken into consideration. Proposed here are two methods which explicitly account for this orientation-induced variation and can robustly determine the structural landscape of a sample ensemble. The first, termed common-line principal component analysis (PCA), provides a rough classification which is essentially parameter free and can be run automatically on any SPI dataset. The second method, utilizing variation auto-encoders (VAEs), can generate 3D structures of the objects at any point in the structural landscape. Both these methods are implemented in combination with the noise-tolerant expand\textendash maximize\textendash compress ( EMC ) algorithm and its utility is demonstrated by applying it to an experimental dataset from gold nanoparticles with only a few thousand photons per pattern. Both discrete structural classes and continuous deformations are recovered. These developments diverge from previous approaches of extracting reproducible subsets of patterns from a dataset and open up the possibility of moving beyond the study of homogeneous sample sets to addressing open questions on topics such as nanocrystal growth and dynamics, as well as phase transitions which have not been externally triggered.},

keywords = {diffractive imaging, nanoparticles, Single-particle imaging, XFEL},

pubstate = {published},

tppubtype = {article}

}

@article{Lubke:J.Phys.Chem.C125:25794,

title = {Charge-State Distribution of Aerosolized Nanoparticles},

author = {Jannik L\"{u}bke and Nils Roth and Lena Worbs and Daniel A. Horke and Armando D. Estillore and Amit K. Samanta and Jochen K\"{u}pper},

url = {https://pubs.acs.org/doi/10.1021/acs.jpcc.1c06912},

doi = {10.1021/acs.jpcc.1c06912},

issn = {1932-7447, 1932-7455},

year  = {2021},

date = {2021-11-01},

urldate = {2022-01-03},

journal = {J. Phys. Chem. C},

volume = {125},

number = {46},

pages = {25794--25798},

abstract = {In single-particle imaging experiments, beams of individual nanoparticles are exposed to intense pulses of X-rays from free-electron lasers to record diffraction patterns of single, isolated molecules. The reconstruction for structure determination relies on signals from many identical particles. Therefore, well-defined-sample delivery conditions are desired in order to achieve sample uniformity, including avoidance of charge polydispersity. We have observed charging of 220 nm polystyrene particles in an aerosol beam created by a gas-dynamic virtual nozzle focusing technique, without intentional charging of the nanoparticles. Here, we present a deflection method for detecting and characterizing the charge states of a beam of aerosolized nanoparticles. Our analysis of the observed charge-state distribution using optical light-sheet localization microscopy and quantitative particle trajectory simulations is consistent with previous descriptions of skewed charging probabilities of triboelectrically charged nanoparticles.},

keywords = {nanoparticles, Single-particle imaging},

pubstate = {published},

tppubtype = {article}

}

@article{Caballo:J.Phys.Chem.A125:9060,

title = {Femtosecond 2 + 1 Resonance-Enhanced Multiphoton Ionization Spectroscopy of the C-State in Molecular Oxygen},

author = {Ana Caballo and Anders J. T. M. Huits and Arno Vredenborg and Michiel Balster and David H. Parker and Daniel A. Horke},

url = {https://doi.org/10.1021/acs.jpca.1c05541},

doi = {10.1021/acs.jpca.1c05541},

issn = {1089-5639},

year  = {2021},

date = {2021-10-01},

journal = {J. Phys. Chem. A},

volume = {125},

number = {41},

pages = {9060--9064},

publisher = {American Chemical Society},

abstract = {Coincidence electron-cation imaging is used to characterize the multiphoton ionization of O2 via the v = 4,5 levels of the 3s(3$Pi$g) Rydberg state. A tunable 100 fs laser beam operating in the 271\textendash 263 nm region is found to cause a nonresonant ionization across this wavelength range, with an additional resonant ionization channel only observed when tuned to the 3$Pi$g(v = 5) level. A distinct 3s textrightarrow p wave character is observed in the photoelectron angular distribution for the v = 5 channel when on resonance.},

keywords = {Coincidence Imaging, Photoelectron spectroscopy, velocity-map imaging},

pubstate = {published},

tppubtype = {article}

}

@article{Ayyer:Optica8:15,

title = {3D Diffractive Imaging of Nanoparticle Ensembles Using an X-Ray Laser},

author = {Kartik Ayyer and P. Lourdu Xavier and Johan Bielecki and Zhou Shen and Benedikt J. Daurer and Amit K. Samanta and Salah Awel and Richard Bean and Anton Barty and Martin Bergemann and Tomas Ekeberg and Armando D. Estillore and Hans Fangohr and Klaus Giewekemeyer and Mark S. Hunter and Mikhail Karnevskiy and Richard A. Kirian and Henry Kirkwood and Yoonhee Kim and Jayanath Koliyadu and Holger Lange and Romain Letrun and Jannik L\"{u}bke and Thomas Michelat and Andrew J. Morgan and Nils Roth and Tokushi Sato and Marcin Sikorski and Florian Schulz and John C. H. Spence and Patrik Vagovic and Tamme Wollweber and Lena Worbs and Oleksandr Yefanov and Yulong Zhuang and Filipe R. N. C. Maia and Daniel A. Horke and Jochen K\"{u}pper and N. Duane Loh and Adrian P. Mancuso and Henry N. Chapman},

url = {https://www.osapublishing.org/abstract.cfm?URI=optica-8-1-15},

doi = {10.1364/OPTICA.410851},

issn = {2334-2536},

year  = {2021},

date = {2021-01-01},

urldate = {2021-06-21},

journal = {Optica},

volume = {8},

number = {1},

pages = {15},

keywords = {diffractive imaging, nanoparticles, Single-particle imaging, XFEL},

pubstate = {published},

tppubtype = {article}

}

@article{Warne:J.Chem.Phys.154:034302,

title = {Time Resolved Detection of the S(1D) Product of the UV Induced Dissociation of CS2},

author = {Emily M. Warne and Adam D. Smith and Daniel A. Horke and Emma Springate and Alfred J. H. Jones and Cephise Cacho and Richard T. Chapman and Russell S. Minns},

url = {http://aip.scitation.org/doi/10.1063/5.0035045},

doi = {10.1063/5.0035045},

issn = {0021-9606, 1089-7690},

year  = {2021},

date = {2021-01-01},

urldate = {2021-06-21},

journal = {J. Chem. Phys.},

volume = {154},

number = {3},

pages = {034302},

abstract = {The products formed following the photodissociation of UV (200 nm) excited CS2 are monitored in a time resolved photoelectron spectroscopy experiment using femtosecond XUV (21.5 eV) photons. By spectrally resolving the electrons, we identify separate photoelectron bands related to the CS2 + h$nu$ textrightarrow S(1D) + CS and CS2 + h$nu$ textrightarrow S(3P) + CS dissociation channels, which show different appearance and rise times. The measurements show that there is no delay in the appearance of the S(1D) product contrary to the results of Horio et al. [J. Chem. Phys. 147, 013932 (2017)]. Analysis of the photoelectron yield associated with the atomic products allows us to obtain a S(3P)/S(1D) branching ratio and the rate constants associated with dissociation and intersystem crossing rather than the effective lifetime observed through the measurement of excited state populations alone.},

keywords = {Coincidence Imaging, dynamics, HHG, Non-adiabatic dynamics, Photoelectron spectroscopy},

pubstate = {published},

tppubtype = {article}

}

@article{Sobolev:CommunPhys3:97,

title = {Megahertz Single-Particle Imaging at the European XFEL},

author = {Egor Sobolev and Sergei Zolotarev and Klaus Giewekemeyer and Johan Bielecki and Kenta Okamoto and Hemanth K. N. Reddy and Jakob Andreasson and Kartik Ayyer and Imrich Barak and Sadia Bari and Anton Barty and Richard Bean and Sergey Bobkov and Henry N. Chapman and Grzegorz Chojnowski and Benedikt J. Daurer and Katerina D\"{o}rner and Tomas Ekeberg and Leonie Fl\"{u}ckiger and Oxana Galzitskaya and Luca Gelisio and Steffen Hauf and Brenda G. Hogue and Daniel A. Horke and Ahmad Hosseinizadeh and Vyacheslav Ilyin and Chulho Jung and Chan Kim and Yoonhee Kim and Richard A. Kirian and Henry Kirkwood and Olena Kulyk and Jochen K\"{u}pper and Romain Letrun and N. Duane Loh and Kristina Lorenzen and Marc Messerschmidt and Kerstin M\"{u}hlig and Abbas Ourmazd and Natascha Raab and Andrei V. Rode and Max Rose and Adam Round and Takushi Sato and Robin Schubert and Peter Schwander and Jonas A. Sellberg and Marcin Sikorski and Alessandro Silenzi and Changyong Song and John C. H. Spence and Stephan Stern and Jolanta Sztuk-Dambietz and Anthon Teslyuk and Nicusor Timneanu and Martin Trebbin and Charlotte Uetrecht and Britta Weinhausen and Garth J. Williams and P. Lourdu Xavier and Chen Xu and Ivan A. Vartanyants and Victor S. Lamzin and Adrian Mancuso and Filipe R. N. C. Maia},

url = {http://www.nature.com/articles/s42005-020-0362-y},

doi = {10.1038/s42005-020-0362-y},

issn = {2399-3650},

year  = {2020},

date = {2020-12-01},

urldate = {2021-06-21},

journal = {Commun Phys},

volume = {3},

number = {1},

pages = {97},

abstract = {Abstract The emergence of high repetition-rate X-ray free-electron lasers (XFELs) powered by superconducting accelerator technology enables the measurement of significantly more experimental data per day than was previously possible. The European XFEL is expected to provide 27,000 pulses per second, over two orders of magnitude more than any other XFEL. The increased pulse rate is a key enabling factor for single-particle X-ray diffractive imaging, which relies on averaging the weak diffraction signal from single biological particles. Taking full advantage of this new capability requires that all experimental steps, from sample preparation and delivery to the acquisition of diffraction patterns, are compatible with the increased pulse repetition rate. Here, we show that single-particle imaging can be performed using X-ray pulses at megahertz repetition rates. The results obtained pave the way towards exploiting high repetition-rate X-ray free-electron lasers for single-particle imaging at their full repetition rate.},

keywords = {diffractive imaging, nanoparticles, Single-particle imaging, XFEL},

pubstate = {published},

tppubtype = {article}

}

@article{Samanta:StructuralDynamics7:024304,

title = {Controlled Beams of Shock-Frozen, Isolated, Biological and Artificial Nanoparticles},

author = {Amit K. Samanta and Muhamed Amin and Armando D. Estillore and Nils Roth and Lena Worbs and Daniel A. Horke and Jochen K\"{u}pper},

url = {https://aca.scitation.org/doi/10.1063/4.0000004},

doi = {10.1063/4.0000004},

year  = {2020},

date = {2020-03-01},

urldate = {2020-07-21},

journal = {Structural Dynamics},

volume = {7},

number = {2},

pages = {024304},

publisher = {American Institute of Physics},

abstract = {X-ray free-electron lasers promise diffractive imaging of single molecules and nanoparticles with atomic spatial resolution. This relies on the averaging of millions of diffraction patterns of identical particles, which should ideally be isolated in the gas phase and preserved in their native structure. Here, we demonstrated that polystyrene nanospheres and Cydia pomonella granulovirus can be transferred into the gas phase, isolated, and very quickly shock-frozen, i.e., cooled to 4,K within microseconds in a helium-buffer-gas cell, much faster than state-of-the-art approaches. Nanoparticle beams emerging from the cell were characterized using particle-localization microscopy with light-sheet illumination, which allowed for the full reconstruction of the particle beams, focused to $\<$100$mu$m$\<$100,$mu$m$\<$math display="inline" overflow="scroll" altimg="eq-00001.gif"$\>$ $\<$mrow$\>$ $\<$mo$\>\&$lt;$\<$/mo$\>$ $\<$mn$\>$100$\<$/mn$\>$ $\<$mo$\>$,$\<$/mo$\>$ $\<$mi$\>mu\<$/mi$\>$ $\<$mi mathvariant="normal"$\>$m$\<$/mi$\>\<$/mrow$\>\<$/math$\>$, as well as for the determination of particle flux and number density. The experimental results were quantitatively reproduced and rationalized through particle-trajectory simulations. We propose an optimized setup with cooling rates for particles of few-nanometers on nanosecond timescales. The produced beams of shock-frozen isolated nanoparticles provide a breakthrough in sample delivery, e.g., for diffractive imaging and microscopy or low-temperature nanoscience.},

keywords = {Control, experimental design, nanoparticles},

pubstate = {published},

tppubtype = {article}

}

@article{Worbs:Opt.Express27:36580,

title = {Light-Sheet Imaging for the Recording of Transverse Absolute Density Distributions of Gas-Phase Particle-Beams from Nanoparticle Injectors},

author = {Lena Worbs and Lena Worbs and Jannik L\"{u}bke and Jannik L\"{u}bke and Jannik L\"{u}bke and Nils Roth and Nils Roth and Amit K. Samanta and Daniel A. Horke and Daniel A. Horke and Daniel A. Horke and Jochen K\"{u}pper and Jochen K\"{u}pper and Jochen K\"{u}pper},

url = {https://www.osapublishing.org/oe/abstract.cfm?uri=oe-27-25-36580},

doi = {10.1364/OE.27.036580},

issn = {1094-4087},

year  = {2019},

date = {2019-12-01},

urldate = {2020-07-21},

journal = {Opt. Express},

volume = {27},

number = {25},

pages = {36580--36586},

publisher = {Optical Society of America},

abstract = {Imaging biological molecules in the gas-phase requires novel sample delivery methods, which generally have to be characterized and optimized to produce high-density particle beams. A non-destructive characterization method of the transverse particle beam profile is presented. It enables the characterization of the particle beam in parallel to the collection of, for instance, x-ray-diffraction patterns. As a rather simple experimental method, it requires the generation of a small laser-light sheet using a cylindrical telescope and a microscope. The working principle of this technique was demonstrated for the characterization of the fluid-dynamic-focusing behavior of 220 nm polystyrene beads as prototypical nanoparticles. The particle flux was determined and the velocity distribution was calibrated using Mie-scattering calculations.},

keywords = {experimental design, nanoparticles, Single-particle imaging},

pubstate = {published},

tppubtype = {article}

}

@article{Bieker:J.Phys.Chem.A123:7486,

title = {Pure Molecular Beam of Water Dimer},

author = {Helen Bieker and Jolijn Onvlee and Melby Johny and Lanhai He and Thomas Kierspel and Sebastian Trippel and Daniel Alfred Horke and Jochen K\"{u}pper},

url = {https://doi.org/10.1021/acs.jpca.9b06460},

doi = {10.1021/acs.jpca.9b06460},

issn = {1089-5639},

year  = {2019},

date = {2019-07-01},

urldate = {2019-08-07},

journal = {J. Phys. Chem. A},

volume = {123},

number = {34},

pages = {7486--7490},

abstract = {Spatial separation of water dimers from water monomers and larger water-clusters through the electric deflector is presented. A beam of water dimers with $93textasciitildetextbackslash%$ purity and a rotational temperature of $1.5textasciitilde$K was obtained. Following strong-field ionization using a 35textasciitilde fs laser pulse with a wavelength centered around 800textasciitilde nm and a peak intensity of $10^14textasciitildetextbackslash Wpcmcm$ we observed proton transfer and $46textasciitildetextbackslash%$ of ionized water dimers broke apart into hydronium ions textbackslash HHHOp and neutral OH.},

keywords = {clusters, Control, electrostatic deflector, strong-field processes},

pubstate = {published},

tppubtype = {article}

}

@article{Roth:JournalofAerosolScience124:17,

title = {Optimizing Aerodynamic Lenses for Single-Particle Imaging},

author = {Nils Roth and Salah Awel and Daniel A. Horke and Jochen K\"{u}pper},

url = {http://www.sciencedirect.com/science/article/pii/S0021850217304652},

doi = {10.1016/j.jaerosci.2018.06.010},

issn = {0021-8502},

year  = {2018},

date = {2018-10-01},

urldate = {2019-01-15},

journal = {Journal of Aerosol Science},

volume = {124},

pages = {17--29},

abstract = {A numerical simulation infrastructure capable of calculating the flow of gas and the trajectories of particles through an aerodynamic lens injector is presented. The simulations increase the fundamental understanding and predict optimized injection geometries and parameters. Our simulation results were compared to previous reports and also validated against experimental data for 500 nm polystyrene spheres from an aerosol-beam-characterization setup. The simulations yielded a detailed understanding of the radial phase-space distribution and highlighted weaknesses of current aerosol injectors for single-particle diffractive imaging. With the aid of these simulations we developed new experimental implementations to overcome current limitations.},

keywords = {experimental design, nanoparticles, Simulation, Single-particle imaging},

pubstate = {published},

tppubtype = {article}

}

@article{Wiedorn:NatureComm.9:4025,

title = {Megahertz Serial Crystallography},

author = {Max O. Wiedorn and Dominik Oberth\"{u}r and Richard Bean and Robin Schubert and Nadine Werner and Brian Abbey and Martin Aepfelbacher and Luigi Adriano and Aschkan Allahgholi and Nasser Al-Qudami and Jakob Andreasson and Steve Aplin and Salah Awel and Kartik Ayyer and Sav sa Bajt and Imrich Bar\'{a}k and Sadia Bari and Johan Bielecki and Sabine Botha and Djelloul Boukhelef and Wolfgang Brehm and Sandor Brockhauser and Igor Cheviakov and Matthew A. Coleman and Francisco Cruz-Mazo and Cyril Danilevski and Connie Darmanin and R. Bruce Doak and Martin Domaracky and Katerina D\"{o}rner and Yang Du and Hans Fangohr and Holger Fleckenstein and Matthias Frank and Petra Fromme and Alfonso M. Ga n\'{a}n-Calvo and Yaroslav Gevorkov and Klaus Giewekemeyer and Helen Mary Ginn and Heinz Graafsma and Rita Graceffa and Dominic Greiffenberg and Lars Gumprecht and Peter G\"{o}ttlicher and Janos Hajdu and Steffen Hauf and Michael Heymann and Susannah Holmes and Daniel A. Horke and Mark S. Hunter and Siegfried Imlau and Alexander Kaukher and Yoonhee Kim and Alexander Klyuev and Juraj Knov ska and Bostjan Kobe and Manuela Kuhn and Christopher Kupitz and Jochen K\"{u}pper and Janine Mia Lahey-Rudolph and Torsten Laurus and Karoline Le Cong and Romain Letrun and P. Lourdu Xavier and Luis Maia and Filipe R. N. C. Maia and Valerio Mariani and Marc Messerschmidt and Markus Metz and Davide Mezza and Thomas Michelat and Grant Mills and Diana C. F. Monteiro and Andrew Morgan and Kerstin M\"{u}hlig and Anna Munke and Astrid M\"{u}nnich and Julia Nette and Keith A. Nugent and Theresa Nuguid and Allen M. Orville and Suraj Pandey and Gisel Pena and Pablo Villanueva-Perez and Jennifer Poehlsen and Gianpietro Previtali and Lars Redecke and Winnie Maria Riekehr and Holger Rohde and Adam Round and Tatiana Safenreiter and Iosifina Sarrou and Tokushi Sato and Marius Schmidt and Bernd Schmitt and Robert Sch\"{o}nherr and Joachim Schulz and Jonas A. Sellberg and M. Marvin Seibert and Carolin Seuring and Megan L. Shelby and Robert L. Shoeman and Marcin Sikorski and Alessandro Silenzi and Claudiu A. Stan and Xintian Shi and Stephan Stern and Jola Sztuk-Dambietz and Janusz Szuba and Aleksandra Tolstikova and Martin Trebbin and Ulrich Trunk and Patrik Vagovic and Thomas Ve and Britta Weinhausen and Thomas A. White and Krzysztof Wrona and Chen Xu and Oleksandr Yefanov and Nadia Zatsepin and Jiaguo Zhang and Markus Perbandt and Adrian P. Mancuso and Christian Betzel and Henry Chapman and Anton Barty},

url = {https://www.nature.com/articles/s41467-018-06156-7},

doi = {10.1038/s41467-018-06156-7},

issn = {2041-1723},

year  = {2018},

date = {2018-10-01},

urldate = {2019-01-24},

journal = {Nature Comm.},

volume = {9},

number = {1},

pages = {4025},

abstract = {The new European X-Ray Free-Electron Laser (EuXFEL) is the first XFEL that generates X-ray pulses with a megahertz inter-pulse spacing. Here the authors demonstrate that high-quality and damage-free protein structures can be obtained with the currently available 1.1 MHz repetition rate pulses using lysozyme as a test case and furthermore present a $beta$-lactamase structure.},

keywords = {crystallography, diffractive imaging, XFEL},

pubstate = {published},

tppubtype = {article}

}

@article{Wiedorn:IUCrJ5:574,

title = {Rapid Sample Delivery for Megahertz Serial Crystallography at X-Ray FELs},

author = {M. O. Wiedorn and S. Awel and A. J. Morgan and K. Ayyer and Y. Gevorkov and H. Fleckenstein and N. Roth and L. Adriano and R. Bean and K. R. Beyerlein and J. Chen and J. Coe and F. Cruz-Mazo and T. Ekeberg and R. Graceffa and M. Heymann and D. A. Horke and J. Knov ska and V. Mariani and R. Nazari and D. Oberth\"{u}r and A. K. Samanta and R. G. Sierra and C. A. Stan and O. Yefanov and D. Rompotis and J. Correa and B. Erk and R. Treusch and J. Schulz and B. G. Hogue and A. M. Ga n\'{a}n-Calvo and P. Fromme and J. K\"{u}pper and A. V. Rode and S. Bajt and R. A. Kirian and H. N. Chapman},

url = {http://scripts.iucr.org/cgi-bin/paper?it5016},

doi = {10.1107/S2052252518008369},

issn = {2052-2525},

year  = {2018},

date = {2018-09-01},

urldate = {2019-01-24},

journal = {IUCrJ},

volume = {5},

number = {5},

pages = {574--584},

abstract = {Liquid microjets are a common means of delivering protein crystals to the focus of X-ray free-electron lasers (FELs) for serial femtosecond crystallography measurements. The high X-ray intensity in the focus initiates an explosion of the microjet and sample. With the advent of X-ray FELs with megahertz rates, the typical velocities of these jets must be increased significantly in order to replenish the damaged material in time for the subsequent measurement with the next X-ray pulse. This work reports the results of a megahertz serial diffraction experiment at the FLASH FEL facility using 4.3hspace0.25emnm radiation. The operation of gas-dynamic nozzles that produce liquid microjets with velocities greater than 80hspace0.25emmhspace0.25ems-1 was demonstrated. Furthermore, this article provides optical images of X-ray-induced explosions together with Bragg diffraction from protein microcrystals exposed to trains of X-ray pulses repeating at rates of up to 4.5hspace0.25emMHz. The results indicate the feasibility for megahertz serial crystallography measurements with hard X-rays and give guidance for the design of such experiments.},

keywords = {crystallography, diffractive imaging, experimental design, Single-particle imaging, XFEL},

pubstate = {published},

tppubtype = {article}

}

@article{Teschmit:Angew.Chem.Int.Ed.57:13775,

title = {Spatially Separating the Conformers of a Dipeptide},

author = {Nicole Teschmit and Daniel A. Horke and Jochen K\"{u}pper},

url = {https://onlinelibrary.wiley.com/doi/full/10.1002/anie.201807646},

doi = {10.1002/anie.201807646},

year  = {2018},

date = {2018-08-01},

journal = {Angew. Chem. Int. Ed.},

volume = {57},

pages = {13775--13779},

keywords = {Control, electrostatic deflector, Isomer-effects, Simulation},

pubstate = {published},

tppubtype = {article}

}

@article{Smith:Phys.Rev.Lett.120:183003,

title = {Mapping the Complete Reaction Path of a Complex Photochemical Reaction},

author = {Adam D. Smith and Emily M. Warne and Darren Bellshaw and Daniel A. Horke and Maria Tudorovskya and Emma Springate and Alfred J. H. Jones and Cephise Cacho and Richard T. Chapman and Adam Kirrander and Russell S. Minns},

url = {https://link.aps.org/doi/10.1103/PhysRevLett.120.183003},

doi = {10.1103/PhysRevLett.120.183003},

year  = {2018},

date = {2018-05-01},

urldate = {2019-01-24},

journal = {Phys. Rev. Lett.},

volume = {120},

number = {18},

pages = {183003},

abstract = {We probe the dynamics of dissociating CS2 molecules across the entire reaction pathway upon excitation. Photoelectron spectroscopy measurements using laboratory-generated femtosecond extreme ultraviolet pulses monitor the competing dissociation, internal conversion, and intersystem crossing dynamics. Dissociation occurs either in the initially excited singlet manifold or, via intersystem crossing, in the triplet manifold. Both product channels are monitored and show that, despite being more rapid, the singlet dissociation is the minor product and that triplet state products dominate the final yield. We explain this by a consideration of accurate potential energy curves for both the singlet and triplet states. We propose that rapid internal conversion stabilizes the singlet population dynamically, allowing for singlet-triplet relaxation via intersystem crossing and the efficient formation of spin-forbidden dissociation products on longer timescales. The study demonstrates the importance of measuring the full reaction pathway for defining accurate reaction mechanisms.},

keywords = {Coincidence Imaging, dynamics, HHG, Non-adiabatic dynamics, Photoelectron spectroscopy},

pubstate = {published},

tppubtype = {article}

}

@article{Singh:Phys.Rev.A97:032704,

title = {Optimized Cell Geometry for Buffer-Gas-Cooled Molecular-Beam Sources},

author = {Vijay Singh and Amit K Samanta and Nils Roth and Daniel Gusa and Tim Ossenbr\"{u}ggen and Igor Rubinsky and Daniel A Horke and Jochen K\"{u}pper},

url = {https://link.aps.org/doi/10.1103/PhysRevA.97.032704},

doi = {10.1103/PhysRevA.97.032704},

year  = {2018},

date = {2018-03-01},

journal = {Phys. Rev. A},

volume = {97},

number = {3},

pages = {032704},

abstract = {We have designed, constructed, and commissioned a cryogenic helium buffer-gas source for producing a cryogenically cooled molecular beam and evaluated the effect of different cell geometries on the intensity of the produced molecular beam, using ammonia as a test molecule. Planar and conical entrance and exit geometries are tested. We observe a threefold enhancement in the $textbackslash mathrmNH_3$ signal for a cell with planar entrance and conical-exit geometry, compared to that for a typically used ``boxlike'' geometry with planar entrance and exit. These observations are rationalized by flow field simulations for the different buffer-gas cell geometries. The full thermalization of molecules with the helium buffer gas is confirmed through rotationally resolved resonance-enhanced multiphoton ionization spectra yielding a rotational temperature of 5 K.},

keywords = {Control, experimental design},

pubstate = {published},

tppubtype = {article}

}

@article{Awel:JApplCryst51:133,

title = {Femtosecond X-Ray Diffraction from an Aerosolized Beam of Protein Nanocrystals},

author = {S. Awel and R. A. Kirian and M. O. Wiedorn and K. R. Beyerlein and N. Roth and D. A. Horke and D. Oberth\"{u}r and J. Knoska and V. Mariani and A. Morgan and L. Adriano and A. Tolstikova and P. L. Xavier and O. Yefanov and A. Aquila and A. Barty and S. Roy-Chowdhury and M. S. Hunter and D. James and J. S. Robinson and U. Weierstall and A. V. Rode and S. Bajt and J. K\"{u}pper and H. N. Chapman},

url = {http://scripts.iucr.org/cgi-bin/paper?te5021},

doi = {10.1107/S1600576717018131},

issn = {1600-5767},

year  = {2018},

date = {2018-02-01},

urldate = {2019-01-24},

journal = {J Appl Cryst},

volume = {51},

number = {1},

pages = {133--139},

abstract = {High-resolution Bragg diffraction from aerosolized single granulovirus nanocrystals using an X-ray free-electron laser is demonstrated. The outer dimensions of the in-vacuum aerosol injector components are identical to conventional liquid-microjet nozzles used in serial diffraction experiments, which allows the injector to be utilized with standard mountings. As compared with liquid-jet injection, the X-ray scattering background is reduced by several orders of magnitude by the use of helium carrier gas rather than liquid. Such reduction is required for diffraction measurements of small macromolecular nanocrystals and single particles. High particle speeds are achieved, making the approach suitable for use at upcoming high-repetition-rate facilities.},

keywords = {diffractive imaging, nanoparticles, Single-particle imaging, XFEL},

pubstate = {published},

tppubtype = {article}

}

@article{Huang:Anal.Chem.90:3920,

title = {Development and Characterization of a Laser-Induced Acoustic Desorption Source},

author = {Zhipeng Huang and Tim Ossenbr\"{u}ggen and Igor Rubinsky and Matthias Schust and Daniel A Horke and Jochen K\"{u}pper},

url = {http://pubs.acs.org/doi/10.1021/acs.analchem.7b04797},

doi = {10.1021/acs.analchem.7b04797},

year  = {2018},

date = {2018-02-01},

journal = {Anal. Chem.},

volume = {90},

number = {6},

pages = {3920--3927},

keywords = {experimental design, LIAD},

pubstate = {published},

tppubtype = {article}

}

@article{Beyerlein:IUCrJ4:769,

title = {Mix-and-Diffuse Serial Synchrotron Crystallography},

author = {K. R. Beyerlein and D. Dierksmeyer and V. Mariani and M. Kuhn and I. Sarrou and A. Ottaviano and S. Awel and J. Knoska and S. Fuglerud and O. J\"{o}nsson and S. Stern and M. O. Wiedorn and O. Yefanov and L. Adriano and R. Bean and A. Burkhardt and P. Fischer and M. Heymann and D. A. Horke and K. E. J. Jungnickel and E. Kovaleva and O. Lorbeer and M. Metz and J. Meyer and A. Morgan and K. Pande and S. Panneerselvam and C. Seuring and A. Tolstikova and J. Lieske and S. Aplin and M. Roessle and T. A. White and H. N. Chapman and A. Meents and D. Oberthuer},

url = {//scripts.iucr.org/cgi-bin/paper?ec5004},

doi = {10.1107/S2052252517013124},

issn = {2052-2525},

year  = {2017},

date = {2017-11-01},

urldate = {2019-01-24},

journal = {IUCrJ},

volume = {4},

number = {6},

pages = {769--777},

abstract = {Unravelling the interaction of biological macromolecules with ligands and substrates at high spatial and temporal resolution remains a major challenge in structural biology. The development of serial crystallography methods at X-ray free-electron lasers and subsequently at synchrotron light sources allows new approaches to tackle this challenge. Here, a new polyimide tape drive designed for mix-and-diffuse serial crystallography experiments is reported. The structure of lysozyme bound by the competitive inhibitor chitotriose was determined using this device in combination with microfluidic mixers. The electron densities obtained from mixing times of 2 and 50hspace0.25ems show clear binding of chitotriose to the enzyme at a high level of detail. The success of this approach shows the potential for high-throughput drug screening and even structural enzymology on short timescales at bright synchrotron light sources.},

keywords = {crystallography, diffractive imaging, nanoparticles},

pubstate = {published},

tppubtype = {article}

}

@article{Wiedorn:JSynchrotronRad24:1296,

title = {Post-Sample Aperture for Low Background Diffraction Experiments at X-Ray Free-Electron Lasers},

author = {M. O. Wiedorn and S. Awel and A. J. Morgan and M. Barthelmess and R. Bean and K. R. Beyerlein and L. M. G. Chavas and N. Eckerskorn and H. Fleckenstein and M. Heymann and D. A. Horke and J. Knov ska and V. Mariani and D. Oberth\"{u}r and N. Roth and O. Yefanov and A. Barty and S. Bajt and J. K\"{u}pper and A. V. Rode and R. A. Kirian and H. N. Chapman},

url = {http://scripts.iucr.org/cgi-bin/paper?gb5058},

doi = {10.1107/S1600577517011961},

issn = {1600-5775},

year  = {2017},

date = {2017-11-01},

urldate = {2019-01-24},

journal = {J Synchrotron Rad},

volume = {24},

number = {6},

pages = {1296--1298},

abstract = {The success of diffraction experiments from weakly scattering samples strongly depends on achieving an optimal signal-to-noise ratio. This is particularly important in single-particle imaging experiments where diffraction signals are typically very weak and the experiments are often accompanied by significant background scattering. A simple way to tremendously reduce background scattering by placing an aperture downstream of the sample has been developed and its application in a single-particle X-ray imaging experiment at FLASH is demonstrated. Using the concept of a post-sample aperture it was possible to reduce the background scattering levels by two orders of magnitude.},

keywords = {experimental design, Single-particle imaging, XFEL},

pubstate = {published},

tppubtype = {article}

}

@article{Teschmit:J.Chem.Phys.147:144204,

title = {Characterizing and Optimizing a Laser-Desorption Molecular Beam Source},

author = {Nicole Teschmit and Karol D\lugo\l\k{e}cki and Daniel Gusa and Igor Rubinsky and Daniel A Horke and Jochen K\"{u}pper},

url = {http://aip.scitation.org/doi/10.1063/1.4991639},

doi = {10.1063/1.4991639},

year  = {2017},

date = {2017-10-01},

journal = {J. Chem. Phys.},

volume = {147},

number = {14},

pages = {144204},

abstract = {The design and characterization of a new laser-desorption molecular beam source, tailored for use in x-ray free-electron laser and ultrashort-pulse laser imaging experiments, is presented. It consists of a single mechanical unit containing all source components, including the molecular-beam valve, the sample, and the fiber-coupled desorption laser, which is movable in five axes, as required for experiments at central facilities. Utilizing strong-field ionization, we characterize the produced molecular beam and evaluate the influence of desorption laser pulse energy, relative timing of valve opening and desorption laser, sample bar height, and which part of the molecular packet is probed on the sample properties. Strong-field ionization acts as a universal probe and allows detecting all species present in the molecular beam, and hence enables us to analyze the purity of the produced molecular beam, including molecular fragments. We present optimized experimental parameters for the production of the purest ...},

keywords = {experimental design},

pubstate = {published},

tppubtype = {article}

}

@article{Bellshaw:Chem.Phys.Lett.683:383,

title = {Ab-Initio Surface Hopping and Multiphoton Ionisation Study of the Photodissociation Dynamics of CS2},

author = {Darren Bellshaw and Daniel A. Horke and Adam D. Smith and Hannah M. Watts and Edward Jager and Emma Springate and Oliver Alexander and Cephise Cacho and Richard T. Chapman and Adam Kirrander and Russell S. Minns},

url = {http://www.sciencedirect.com/science/article/pii/S0009261417301744},

doi = {10.1016/j.cplett.2017.02.058},

issn = {0009-2614},

year  = {2017},

date = {2017-09-01},

urldate = {2019-01-24},

journal = {Chem. Phys. Lett.},

volume = {683},

pages = {383--388},

series = {Ahmed Zewail (1946-2016) Commemoration Issue of Chemical Physics Letters},

abstract = {New ab initio surface hopping simulations of the excited state dynamics of CS2 including spin-orbit coupling are compared to new experimental measurements using a multiphoton ionisation probe in a photoelectron spectroscopy experiment. The calculations highlight the importance of the triplet states even in the very early time dynamics of the dissociation process and allow us to unravel the signatures in the experimental spectrum, linking the observed changes to both electronic and nuclear degrees of freedom within the molecule.},

keywords = {dynamics, Non-adiabatic dynamics, Photoelectron spectroscopy, velocity-map imaging},

pubstate = {published},

tppubtype = {article}

}

@article{Horke:JournalofAppliedPhysics121:123106,

title = {Characterizing Gas Flow from Aerosol Particle Injectors},

author = {Daniel A Horke and Nils Roth and Lena Worbs and Jochen K\"{u}pper},

url = {http://aip.scitation.org/doi/10.1063/1.4978914},

doi = {10.1063/1.4978914},

year  = {2017},

date = {2017-03-01},

journal = {Journal of Applied Physics},

volume = {121},

number = {12},

pages = {123106},

keywords = {experimental design, nanoparticles},

pubstate = {published},

tppubtype = {article}

}

@article{Horke:Phys.Rev.Lett.117:163002,

title = {Hydrogen Bonds in Excited State Proton Transfer},

author = {D A Horke and H M Watts and A D Smith and E Jager and E Springate and O Alexander and C Cacho and R T Chapman and R S Minns},

url = {http://link.aps.org/doi/10.1103/PhysRevLett.117.163002},

doi = {10.1103/PhysRevLett.117.163002},

year  = {2016},

date = {2016-10-01},

journal = {Phys. Rev. Lett.},

volume = {117},

number = {16},

pages = {163002},

abstract = {Hydrogen bonding may safeguard biomolecules against the damaging effects of UV light.},

keywords = {Coincidence Imaging, intramolecular interactions, Isomer-effects, Non-adiabatic dynamics, photoelectron imaging, Photoelectron spectroscopy, velocity-map imaging},

pubstate = {published},

tppubtype = {article}

}

@article{Smith:Phys.Chem.Chem.Phys.18:28150,

title = {Resonant Multiphoton Ionisation Probe of the Photodissociation Dynamics of Ammonia},

author = {Adam D Smith and Hannah M Watts and Edward Jager and Daniel A Horke and Emma Springate and Oliver Alexander and Cephise Cacho and Richard T Chapman and Russell S Minns},

url = {http://pubs.rsc.org/en/content/articlehtml/2016/cp/c6cp05279g},

doi = {10.1039/C6CP05279G},

year  = {2016},

date = {2016-10-01},

journal = {Phys. Chem. Chem. Phys.},

volume = {18},

number = {40},

pages = {28150--28156},

abstract = {The dissociation dynamics of the ~A-state of ammonia have been studied using a resonant multiphoton ionisation probe in a photoelectron spectroscopy experiment. The use of a resonant intermediate in the multiphoton ionisation process changes the ionisation propensity, allowing access to different ion states when compared with equivalent single photon ionisation experiments. Ionisation through the E$'$ 1A1$'$ Rydberg intermediate means we maintain overlap with the ion state for an extended period, allowing us to monitor the excited state population for several hundred femtoseconds. The vibrational states in the photoelectron spectrum show two distinct timescales, 200 fs and 320 fs, that we assign to the non-adiabatic and adiabatic dissociation processes respectively. The different timescales derive from differences in the wavepacket trajectories for the two dissociation pathways that resonantly excite different vibrational states in the intermediate Rydberg state. The timescales are similar to those obtained from time resolved ion kinetic energy release measurements, suggesting we can measure the different trajectories taken out to the region of conical intersection.},

keywords = {dynamics, Non-adiabatic dynamics, photoelectron imaging, Photoelectron spectroscopy, velocity-map imaging},

pubstate = {published},

tppubtype = {article}

}

@article{Awel:OpticsExpress24:6507,

title = {Visualizing Aerosol-Particle Injection for Diffractive-Imaging Experiments},

author = {Salah Awel and Richard A Kirian and Niko Eckerskorn and Max Wiedorn and Daniel A Horke and Andrei V Rode and Jochen K\"{u}pper and Henry N Chapman},

url = {http://www.osapublishing.org/viewmedia.cfm?uri=oe-24-6-6507\&seq=0\&html=true},

doi = {10.1364/OE.24.006507},

year  = {2016},

date = {2016-03-01},

journal = {Optics Express},

volume = {24},

number = {6},

pages = {6507--6521},

abstract = {Delivering sub-micrometer particles to an intense x-ray focus is a crucial aspect of single-particle diffractive-imaging experiments at x-ray free-electron lasers. Enabling direct visualization of sub-micrometer aerosol particle streams without interfering with the operation of the particle injector can greatly improve the overall efficiency of single-particle imaging experiments by reducing the amount of time and sample consumed during measurements. We have developed in-situ non-destructive imaging diagnostics to aid real-time particle injector optimization and x-ray/particle-beam alignment, based on laser illumination schemes and fast imaging detectors. Our diagnostics are constructed to provide a non-invasive rapid feedback on injector performance during measurements, and have been demonstrated during diffraction measurements at the FLASH free-electron laser.},

keywords = {diffractive imaging, experimental design, nanoparticles},

pubstate = {published},

tppubtype = {article}

}

@article{Kupper:NachrichtenausderChemie64:319,

title = {Kontrollierte Molek\"{u}le F\"{u}r Beobachtungen von Struktur Und Dynamik},

author = {Jochen K\"{u}pper and Sebastian Trippel and Daniel Horke},

url = {http://onlinelibrary.wiley.com/doi/10.1002/nadc.20164047276/full},

doi = {10.1002/nadc.20164047276},

year  = {2016},

date = {2016-03-01},

journal = {Nachrichten aus der Chemie},

volume = {64},

number = {3},

pages = {319--322},

keywords = {outreach},

pubstate = {published},

tppubtype = {article}

}

@article{Rothhardt:OpticsExpress24:18133,

title = {High-Repetition-Rate and High-Photon-Flux 70 eV High-Harmonic Source for Coincidence Ion Imaging of Gas-Phase Molecules},

author = {Jan Rothhardt and Steffen H\"{a}drich and Yariv Shamir and Maxim Tschnernajew and Robert Klas and Armin Hoffmann and Getnet K Tadesse and Arno Klenke and Thomas Gottschall and Tino Eidam and Jens Limpert and Andreas T\"{u}nnermann and Rebecca Boll and Cedric Bomme and Hatem Dachraoui and Benjamin Erk and Michele Di Fraia and Daniel A Horke and Thomas Kierspel and Terence Mullins and Andreas Przystawik and Evgeny Savelyev and Joss Wiese and Tim Laarmann and Jochen K\"{u}pper and Daniel Rolles},

url = {https://www.osapublishing.org/abstract.cfm?URI=oe-24-16-18133},

doi = {10.1364/OE.24.018133},

year  = {2016},

date = {2016-01-01},

journal = {Optics Express},

volume = {24},

number = {16},

pages = {18133--18147},

abstract = {Unraveling and controlling chemical dynamics requires techniques to image structural changes of molecules with femtosecond temporal and picometer spatial resolution. Ultrashort-pulse x-ray free-electron lasers have significantly advanced the field by enabling advanced pump-probe schemes. There is an increasing interest in using table-top photon sources enabled by high-harmonic generation of ultrashort-pulse lasers for such studies. We present a novel high-harmonic source driven by a 100 kHz fiber laser system, which delivers 1011 photons/s in a single 1.3 eV bandwidth harmonic at 68.6 eV. The combination of record-high photon flux and high repetition rate paves the way for time-resolved studies of the dissociation dynamics of inner-shell ionized molecules in a coincidence detection scheme. First coincidence measurements on CH3I are shown and it is outlined how the anticipated advancement of fiber laser technology and improved sample delivery will, in the next step, allow pump-probe studies of ultrafast molecular dynamics with table-top XUV-photon sources. These table-top sources can provide significantly higher repetition rates than the currently operating free-electron lasers and they offer very high temporal resolution due to the intrinsically small timing jitter between pump and probe pulses.},

keywords = {Coincidence Imaging, HHG, velocity-map imaging},

pubstate = {published},

tppubtype = {article}

}

@article{Chang:Int.Rev.Phys.Chem.34:557,

title = {Spatially-Controlled Complex Molecules and Their Applications},

author = {Yuan-Pin Chang and Daniel A Horke and Sebastian Trippel and Jochen K\"{u}pper},

url = {http://www.tandfonline.com/doi/full/10.1080/0144235X.2015.1077838},

doi = {10.1080/0144235X.2015.1077838},

year  = {2015},

date = {2015-10-01},

journal = {Int. Rev. Phys. Chem.},

volume = {34},

number = {4},

pages = {557--590},

keywords = {clusters, electrostatic deflector, Isomer-effects, review},

pubstate = {published},

tppubtype = {article}

}

@article{Kirian:StructuralDynamics2:041717,

title = {Simple Convergent-Nozzle Aerosol Injector for Single-Particle Diffractive Imaging with X-Ray Free-Electron Lasers},

author = {R A Kirian and S Awel and N Eckerskorn and H Fleckenstein and M Wiedorn and L Adriano and S Bajt and M Barthelmess and R Bean and K R Beyerlein and L M G Chavas and M Domaracky and M Heymann and D A Horke and J Knoska and M Metz and A Morgan and D Oberthuer and N Roth and T Sato and P L Xavier and O Yefanov and A V Rode and J Kupper and H N Chapman},

url = {http://scitation.aip.org/content/aca/journal/sdy/2/4/10.1063/1.4922648},

doi = {10.1063/1.4922648},

year  = {2015},

date = {2015-07-01},

journal = {Structural Dynamics},

volume = {2},

number = {4},

pages = {041717},

keywords = {diffractive imaging, experimental design, nanoparticles, Single-particle imaging, XFEL},

pubstate = {published},

tppubtype = {article}

}

@article{Horke:J.Phys.Chem.Lett.6:189,

title = {Time-Resolved Photodetachment Anisotropy: Gas-Phase Rotational and Vibrational Dynamics of the Fluorescein Anion},

author = {Daniel A Horke and Adam S Chatterley and James N Bull and Jan R R Verlet},

url = {http://pubs.acs.org/doi/abs/10.1021/jz5022526},

doi = {10.1021/jz5022526},

year  = {2015},

date = {2015-01-01},

journal = {J. Phys. Chem. Lett.},

volume = {6},

number = {1},

pages = {189--194},

abstract = {The photoelectron signal of the singly deprotonated fluorescein anion is found to be highly dependent on the relative polarization between pump and probe pulses, and time-resolved photodetachment anisotropy (TR-PA) is developed as a probe of the rotational dynamics of the chromophore. The total photoelectron signal shows both rotational and vibrational wavepacket dynamics, and we demonstrate how TR-PA can readily disentangle these dynamical processes. TR-PA in fluorescein presents specific opportunities for its development as a probe for rotational dynamics in large biomolecules as fluorescein derivatives are commonly incorporated in complex biomolecules and have been used extensively in time-resolved fluorescence anisotropy measurements, to which TR-PA is a gas-phase analogue.},

keywords = {alignment, Anion spectroscopy, photoelectron imaging, Photoelectron spectroscopy, velocity-map imaging},

pubstate = {published},

tppubtype = {article}

}

@article{Horke:Angew.Chem.Int.Ed.53:11965,

title = {Separating Para and Ortho Water},

author = {Daniel A Horke and Yuan-Pin Chang and Karol D\lugo\l\k{e}cki and Jochen K\"{u}pper},

url = {http://onlinelibrary.wiley.com/doi/10.1002/anie.201405986/full},

doi = {10.1002/anie.201405986},

year  = {2014},

date = {2014-10-01},

journal = {Angew. Chem. Int. Ed.},

volume = {53},

number = {44},

pages = {11965--11968},

keywords = {Control, electrostatic deflector, Simulation},

pubstate = {published},

tppubtype = {article}

}

@article{Horke:AngewandteChemie126:12159,

title = {Trennung von Para-und ortho-Wasser},

author = {Daniel A Horke and Yuan-Pin Chang and Karol D\lugo\l\k{e}cki and Jochen K\"{u}pper},

url = {http://onlinelibrary.wiley.com/doi/10.1002/ange.201405986/full},

doi = {10.1002/ange.201405986},

year  = {2014},

date = {2014-10-01},

journal = {Angewandte Chemie},

volume = {126},

number = {44},

pages = {12159--12162},

keywords = {Control, electrostatic deflector, Simulation},

pubstate = {published},

tppubtype = {article}

}

@article{Chatterley:Phys.Chem.Chem.Phys.16:489,

title = {Effects of Resonant Excitation, Pulse Duration and Intensity on Photoelectron Imaging of a Dianion},

author = {Adam S Chatterley and Daniel A Horke and Jan R R Verlet},

url = {http://xlink.rsc.org/?DOI=c3cp53235f},

doi = {10.1039/c3cp53235f},

year  = {2014},

date = {2014-01-01},

journal = {Phys. Chem. Chem. Phys.},

volume = {16},

number = {2},

pages = {489--496},

abstract = {The photoelectron imaging of the indigo carmine dianion is used to demonstrate the effects of resonance excitation, pulse duration and pulse intensity on the photoelectron spectra and angular distributions of a dianion. Excitation of the S1 state leads to an aligned distribution of excited state dianions. The photoelectron angular distribution following subsequent photodetachment within a femtosecond laser pulse is primarily determined by the repulsive Coulomb barrier. Extending the timescale for photodetachment to nanoseconds leads to dramatic changes in both the spectral and angular distributions. These observations are explained in terms of statistical detachment of electrons, either from the monoanion, or from the ground state of the dianion following a number of photon cycles through the S1 $\leftarrow$ S0 transition. At high intensity, new electron emission channels open up, leading to emission below the repulsive Coulomb barrier. This has been assigned to strong-field induced detachment and the effect of an electric field on the Coulomb barrier is discussed in terms of the photoelectron spectra and angular distributions.},

keywords = {Anion spectroscopy, photoelectron imaging, Photoelectron spectroscopy, polyanions, velocity-map imaging},

pubstate = {published},

tppubtype = {article}

}

@article{Horke:JoVE:e51137,

title = {Spatial Separation of Molecular Conformers and Clusters},

author = {Daniel Horke and Sebastian Trippel and Yuan-Pin Chang and Stephan Stern and Terry Mullins and Thomas Kierspel and Jochen K 252 pper},

url = {http://www.jove.com/video/51137},

issn = {1940-087X},

year  = {2014},

date = {2014-01-01},

journal = {JoVE},

number = {83},

pages = {e51137},

abstract = {Gas-phase molecular physics and physical chemistry experiments commonly use supersonic expansions through pulsed valves for the production of cold molecular beams. However, these beams often contain multiple conformers and clusters, even at low rotational temperatures. We present an experimental methodology that allows the spatial separation of these constituent parts of a molecular beam expansion. Using an electric deflector the beam is separated by its mass-to-dipole moment ratio, analogous to a bender or an electric sector mass spectrometer spatially dispersing charged molecules on the basis of their mass-to-charge ratio. This deflector exploits the Stark effect in an inhomogeneous electric field and allows the separation of individual species of polar neutral molecules and clusters. It furthermore allows the selection of the coldest part of a molecular beam, as low-energy rotational quantum states generally experience the largest deflection. Different structural isomers (conformers) of a species can be separated due to the different arrangement of functional groups, which leads to distinct dipole moments. These are exploited by the electrostatic deflector for the production of a conformationally pure sample from a molecular beam. Similarly, specific cluster stoichiometries can be selected, as the mass and dipole moment of a given cluster depends on the degree of solvation around the parent molecule. This allows experiments on specific cluster sizes and structures, enabling the systematic study of solvation of neutral molecules.},

keywords = {clusters, Control, electrostatic deflector, Isomer-effects},

pubstate = {published},

tppubtype = {article}

}

@article{Kierspel:Chem.Phys.Lett.591:130,

title = {Spatially Separated Polar Samples of the Cis and Trans Conformers of 3-Fluorophenol},

author = {Thomas Kierspel and Daniel A Horke and Yuan-Pin Chang and Jochen K\"{u}pper},

url = {http://www.sciencedirect.com/science/article/pii/S0009261413014000},

doi = {10.1016/j.cplett.2013.11.010},

year  = {2014},

date = {2014-01-01},

journal = {Chem. Phys. Lett.},

volume = {591},

number = {0},

pages = {130--132},

keywords = {Control, electrostatic deflector, Isomer-effects, Simulation},

pubstate = {published},

tppubtype = {article}

}

@article{Verlet:Phys.Chem.Chem.Phys.16:15043,

title = {Excited States of Multiply-Charged Anions Probed by Photoelectron Imaging: Riding the Repulsive Coulomb Barrier},

author = {Jan R R Verlet and Daniel A Horke and Adam S Chatterley},

url = {http://xlink.rsc.org/?DOI=c4cp01667j},

doi = {10.1039/c4cp01667j},

year  = {2014},

date = {2014-01-01},

journal = {Phys. Chem. Chem. Phys.},

volume = {16},

number = {29},

pages = {15043--15052},

abstract = {Many properties of isolated multiply-charged anions (MCAs) are dictated by the strong intra-molecular Coulomb interactions that are present. The most striking property of MCAs is a long-range repulsive Coulomb barrier (RCB) that arises from the repulsive interaction between an electron and an anion which must be overcome to form a MCA. Excited states provide a route to probing this RCB and the focus of this Perspective is on recent photoelectron experiments, including angularly and temporally resolved, that have provided detailed physical insight into the RCB surfaces, their anisotropy, and their use to monitor molecular dynamics in real-time. An outlook provides some future prospects that studies on MCAs provide in terms of monitoring structural, charge-migration, and solvation dynamics.},

keywords = {Anion spectroscopy, photoelectron imaging, Photoelectron spectroscopy, review},

pubstate = {published},

tppubtype = {article}

}

@article{Horke:NatureChem.5:711,

title = {Ultrafast Above-Threshold Dynamics of the Radical Anion of a Prototypical Quinone Electron-Acceptor},

author = {Daniel A Horke and Quansong Li and Llu A Blancafort and Jan R R Verlet},

url = {http://dx.doi.org/10.1038/nchem.1705},

doi = {10.1038/nchem.1705},

year  = {2013},

date = {2013-09-01},

urldate = {2013-09-01},

journal = {Nature Chem.},

volume = {5},

number = {8},

pages = {711--717},

keywords = {dynamics, Non-adiabatic dynamics, photoelectron imaging, Photoelectron spectroscopy, velocity-map imaging},

pubstate = {published},

tppubtype = {article}

}

@article{Horke:J.Chem.Phys.139:084302,

title = {Influence of the Repulsive Coulomb Barrier on Photoelectron Spectra and Angular Distributions in a Resonantly Excited Dianion},

author = {Daniel A Horke and Adam S Chatterley and Jan R R Verlet},

url = {http://dx.doi.org/10.1063/1.4818597},

doi = {10.1063/1.4818597},

year  = {2013},

date = {2013-01-01},

journal = {J. Chem. Phys.},

volume = {139},

number = {8},

pages = {084302--10},

keywords = {Anion spectroscopy, photoelectron imaging, Photoelectron spectroscopy, polyanions, velocity-map imaging},

pubstate = {published},

tppubtype = {article}

}

@article{Mooney:Chem.Sci.4:921,

title = {Taking the Green Fluorescence out of the Protein: Dynamics of the Isolated GFP Chromophore Anion},

author = {Ciar\'{a}n R S Mooney and Daniel A Horke and Adam S Chatterley and Alexandra Simperler and Helen H Fielding and Jan R R Verlet},

url = {http://xlink.rsc.org/?DOI=c2sc21737f},

doi = {10.1039/c2sc21737f},

year  = {2013},

date = {2013-01-01},

journal = {Chem. Sci.},

volume = {4},

number = {3},

pages = {921},

keywords = {Anion spectroscopy, dynamics, Non-adiabatic dynamics, photoelectron imaging, Photoelectron spectroscopy, velocity-map imaging},

pubstate = {published},

tppubtype = {article}

}

@article{Horke:J.Phys.Chem.Lett.3:834,

title = {Femtosecond Photoelectron Imaging of Aligned Polyanions: Probing Molecular Dynamics through the Electron\textendashAnion Coulomb Repulsion},

author = {Daniel. A. Horke and Adam S. Chatterley and Jan R. R. Verlet},

url = {https://doi.org/10.1021/jz3000933},

doi = {10.1021/jz3000933},

issn = {1948-7185},

year  = {2012},

date = {2012-04-01},

urldate = {2019-04-03},

journal = {J. Phys. Chem. Lett.},

volume = {3},

number = {7},

pages = {834--838},

abstract = {The first time-resolved photoelectron imaging study of a polyanion is presented. Using the alignment induced through resonance excitation, the photoelectron angular distributions can be qualitatively understood in terms of the position of localized excess charges on the molecular skeleton, which influence the photoemission dynamics. Pump\textendash probe experiments are used to demonstrate that the photoelectron angular distribution is also sensitive to molecular dynamics. This is shown here for the rotational dynamics of a polyanion, in which the photoelectron anisotropy tracks the rotational coherence as it dephases. The methodology can in principle be applied to general molecular dynamics in large polyanions, providing a new route to studying ultrafast structural dynamics in complex gas-phase systems.},

keywords = {alignment, Anion spectroscopy, photoelectron imaging, Photoelectron spectroscopy, velocity-map imaging},

pubstate = {published},

tppubtype = {article}

}