Publications
304 results found
Hutchison CDM, Baxter JM, Fitzpatrick A, et al., 2023, Optical control of ultrafast structural dynamics in a fluorescent protein., Nat Chem
The photoisomerization reaction of a fluorescent protein chromophore occurs on the ultrafast timescale. The structural dynamics that result from femtosecond optical excitation have contributions from vibrational and electronic processes and from reaction dynamics that involve the crossing through a conical intersection. The creation and progression of the ultrafast structural dynamics strongly depends on optical and molecular parameters. When using X-ray crystallography as a probe of ultrafast dynamics, the origin of the observed nuclear motions is not known. Now, high-resolution pump-probe X-ray crystallography reveals complex sub-ångström, ultrafast motions and hydrogen-bonding rearrangements in the active site of a fluorescent protein. However, we demonstrate that the measured motions are not part of the photoisomerization reaction but instead arise from impulsively driven coherent vibrational processes in the electronic ground state. A coherent-control experiment using a two-colour and two-pulse optical excitation strongly amplifies the X-ray crystallographic difference density, while it fully depletes the photoisomerization process. A coherent control mechanism was tested and confirmed the wave packets assignment.
Grell G, Guo Z, Driver T, et al., 2023, Effect of the shot-to-shot variation on charge migration induced by sub-fs x-ray free-electron laser pulses, Physical Review Research, Vol: 5, ISSN: 2643-1564
X-ray free-electron lasers (XFELs) are now able to provide tunable pairs of intense sub-fs pulses in the soft x-ray regime, paving the way for time-resolved investigations of attosecond charge migration in molecules. However, the stochastic shot-to-shot variation of the XFEL pulses may degrade and eventually hide the observable features. We show by means of state-of-the-art calculations that the damping of the charge migration induced by 260 eV pulses in p-aminophenol due to the shot-to-shot variation of pulses generated at the Linac Coherent Light Source is negligible in comparison to the natural damping due to the intrinsic fluctuation of the initial molecular geometry. This result gives us confidence in the utility of XFEL sub-fs pulses for the measurement of charge migration and other ultrafast charge dynamics.
Barnard J, Lee J, Alexander O, et al., 2022, Delivery of stable ultra-thin liquid sheets in vacuum for biochemical spectroscopy, Frontiers in Molecular Biosciences, Vol: 9, ISSN: 2296-889X
The development of ultra-thin flat liquid sheets capable of running in vacuum has provided an exciting new target for X-ray absorption spectroscopy in the liquid and solution phases. Several methods have become available for delivering in-vacuum sheet jets using different nozzle designs. We compare the sheets produced by two different types of nozzle; a commercially available borosillicate glass chip using microfluidic channels to deliver colliding jets, and an in-house fabricated fan spray nozzle which compresses the liquid on an axis out of a slit to achieve collision conditions. We find in our tests that both nozzles are suitable for use in X-ray absorption spectroscopy with the fan spray nozzle producing thicker but more stable jets than the commercial nozzle. We also provide practical details of how to run these nozzles in vacuum.
Schwickert D, Ruberti M, Kolorenc P, et al., 2022, Charge-induced chemical dynamics in glycine probed with time-resolved Auger electron spectroscopy, STRUCTURAL DYNAMICS-US, Vol: 9
Ferchaud C, Jarosch S, Avni T, et al., 2022, Interaction of an intense few-cycle infrared laser pulse with an ultrathin transparent liquid sheet, Optics Express, Vol: 30, Pages: 34684-34692, ISSN: 1094-4087
We experimentally study the interaction between intense infrared few-cycle laser pulses and an ultrathin (∼2 µm) flat liquid sheet of isopropanol running in vacuum. We observe a rapid decline in transmission above a critical peak intensity of 50 TW/cm2 of the initially transparent liquid sheet, and the emission of a plume of material. We find both events are due to the creation of a surface plasma and are similar to processes observed in dielectric solids. After calculating the electron density for different laser peak intensities, we find an electron scattering rate of 0.3 fs-1 in liquid isopropanol to be consistent with our data. We study the dynamics of the plasma plume to find the expansion velocity of the plume front.
Danilov D, Tran T, Bearpark MJJ, et al., 2022, How electronic superpositions drive nuclear motion following the creation of a localized hole in the glycine radical cation, JOURNAL OF CHEMICAL PHYSICS, Vol: 156, ISSN: 0021-9606
Garratt D, Misiekis L, Wood D, et al., 2022, Direct observation of ultrafast exciton localization in an organic semiconductor with soft X-ray transient absorption spectroscopy, Nature Communications, Vol: 13, ISSN: 2041-1723
The localization dynamics of excitons in organic semiconductors influence the efficiency of charge transfer and separation in these materials. Here we apply time-resolved X-ray absorption spectroscopy to track photoinduced dynamics of a paradigmatic crystalline conjugated polymer: poly(3-hexylthiophene) (P3HT) commonly used in solar cell devices. The π→π* transition, the first step of solar energy conversion, is pumped with a 15 fs optical pulse and the dynamics are probed by an attosecond soft X-ray pulse at the carbon K-edge. We observe X-ray spectroscopic signatures of the initially hot excitonic state, indicating that it is delocalized over multiple polymer chains. This undergoes a rapid evolution on a sub 50 fs timescale which can be directly associated with cooling and localization to form either a localized exciton or polaron pair.
Schwickert D, Ruberti M, Kolorenc P, et al., 2022, Electronic quantum coherence in glycine molecules probed with ultrashort x-ray pulses in real time, SCIENCE ADVANCES, Vol: 8, ISSN: 2375-2548
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- Citations: 6
Li S, Driver T, Rosenberger P, et al., 2022, Attosecond coherent electron motion in Auger-Meitner decay, SCIENCE, Vol: 375, Pages: 285-+, ISSN: 0036-8075
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- Citations: 11
Driver T, Bachhawat N, Pipkorn R, et al., 2021, Proteomic Database Search Engine for Two-Dimensional Partial Covariance Mass Spectrometry, ANALYTICAL CHEMISTRY, Vol: 93, Pages: 14946-14954, ISSN: 0003-2700
Barillot T, Alexander O, Cooper B, et al., 2021, Correlation-driven transient hole dynamics resolved in space and time in the isopropanol molecule, Physical Review X, Vol: 11, Pages: 1-15, ISSN: 2160-3308
The possibility of suddenly ionized molecules undergoing extremely fast electron hole (or, hole)dynamics prior to significant structural change was first recognized more than 20 years ago andtermed charge migration. The accurate probing of ultrafast electron hole dynamics requires measurements that have both sufficient temporal resolution and can detect the localization of a specifichole within the molecule. We report an investigation of the dynamics of inner valence hole states inisopropanol where we use an x-ray pump/x-ray probe experiment, with site and state-specific probing of a transient hole state localized near the oxygen atom in the molecule, together with an abinitio theoretical treatment. We record the signature of transient hole dynamics and make the firsttentative observation of dynamics driven by frustrated Auger-Meitner transitions. We verify thatthe effective hole lifetime is consistent with our theoretical prediction. This state-specific measurement paves the way to widespread application for observations of transient hole dynamics localizedin space and time in molecules and thus to charge transfer phenomena that are fundamental inchemical and material physics.
Driver T, Averbukh V, Frasiński LJ, et al., 2021, Two-dimensional partial covariance mass spectrometry for the top-down analysis of intact proteins., Analytical Chemistry, Vol: 93, Pages: 10779-10788, ISSN: 0003-2700
Two-dimensional partial covariance mass spectrometry (2D-PC-MS) exploits the inherent fluctuations of fragment ion abundances across a series of tandem mass spectra, to identify correlated pairs of fragment ions produced along the same fragmentation pathway of the same parent (e.g., peptide) ion. Here, we apply 2D-PC-MS to the analysis of intact protein ions in a standard linear ion trap mass analyzer, using the fact that the fragment-fragment correlation signals are much more specific to the biomolecular sequence than one-dimensional (1D) tandem mass spectrometry (MS/MS) signals at the same mass accuracy and resolution. We show that from the distribution of signals on a 2D-PC-MS map it is possible to extract the charge state of both parent and fragment ions without resolving the isotopic envelope. Furthermore, the 2D map of fragment-fragment correlations naturally separates the products of the primary decomposition pathways of the molecular ions from those of the secondary ones. We access this spectral information using an adapted version of the Hough transform. We demonstrate the successful identification of highly charged, intact protein molecules bypassing the need for high mass resolution. Using this technique, we also perform the in silico deconvolution of the overlapping fragment ion signals from two co-isolated and co-fragmented intact proteins, demonstrating a viable new method for the concurrent mass spectrometric identification of a mixture of intact protein ions from the same fragment ion spectrum.
Li S, Driver T, Al Haddad A, et al., 2021, Two-dimensional correlation analysis for x-ray photoelectron spectroscopy, Journal of Physics B: Atomic, Molecular and Optical Physics, Vol: 54, Pages: 1-9, ISSN: 0953-4075
X-ray photoelectron spectroscopy (XPS) measures the binding energy of core-level electrons, which are well-localised to specific atomic sites in a molecular system, providing valuable information on the local chemical environment. The technique relies on measuring the photoelectron spectrum upon x-ray photoionisation, and the resolution is often limited by the bandwidth of the ionising x-ray pulse. This is particularly problematic for time-resolved XPS, where the desired time resolution enforces a fundamental lower limit on the bandwidth of the x-ray source. In this work, we report a novel correlation analysis which exploits the correlation between the x-ray and photoelectron spectra to improve the resolution of XPS measurements. We show that with this correlation-based spectral-domain ghost imaging method we can achieve sub-bandwidth resolution in XPS measurements. This analysis method enables XPS for sources with large bandwidth or spectral jitter, previously considered unfeasible for XPS measurements.
Driver T, Bachhawat N, Frasinski L, et al., 2021, Chimera spectrum diagnostics for peptides using two-dimensional partial covariance mass spectrometry, Molecules, Vol: 26, ISSN: 1420-3049
The rate of successful identification of peptide sequences by tandem mass spectrometry (MS/MS) is adversely affected by the common occurrence of co-isolation and co-fragmentation of two or more isobaric or isomeric parent ions. This results in so-called `chimera spectra’, which feature peaks of the fragment ions from more than a single precursor ion. The totality of the fragment ion peaks in chimera spectra cannot be assigned to a single peptide sequence, which contradicts a fundamental assumption of the standard automated MS/MS spectra analysis tools, such as protein database search engines. This calls for a diagnostic method able to identify chimera spectra to single out the cases where this assumption is not valid. Here, we demonstrate that, within the recently developed two-dimensional partial covariance mass spectrometry (2D-PC-MS), it is possible to reliably identify chimera spectra directly from the two-dimensional fragment ion spectrum, irrespective of whether the co-isolated peptide ions are isobaric up to a finite mass accuracy or isomeric. We introduce ‘3-57 chimera tag’ technique for chimera spectrum diagnostics based on 2D-PC-MS and perform numerical simulations to examine its efficiency. We experimentally demonstrate the detection of a mixture of two isomeric parent ions, even under conditions when one isomeric peptide is at one five-hundredth of the molar concentration of the second isomer.
Li S, Driver T, Alexander O, et al., 2021, Time-resolved pump-probe spectroscopy with spectral domain ghost imaging, FARADAY DISCUSSIONS, Vol: 228, Pages: 488-501, ISSN: 1359-6640
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- Citations: 10
Austin D, Johnson A, McGrath F, et al., 2021, Extracting sub-cycle electronic and nuclear dynamics from high harmonic spectra, Scientific Reports, Vol: 11, ISSN: 2045-2322
We present a new methodology for measuring few-femtosecond electronic and nuclear dynamics in both atoms and polyatomic molecules using multidimensional high harmonic generation (HHG) spectroscopy measurements, in which the spectra are recorded as a function of the laser intensity to form a two-dimensional data set. The method is applied to xenon atoms and to benzene molecules, the latter exhibiting significant fast nuclear dynamics following ionization. We uncover the signature of the sub-cycle evolution of the returning electron flux in strong-field ionized xenon atoms, implicit in the strong field approximation but not previously observed directly. We furthermore extract the nuclear autocorrelation function in strong field ionized benzene cations, which is determined to have a decay of τ0=4±1 fs, in good agreement with the τ0=3.5 fs obtained from direct dynamics variational multi-configuration Gaussian calculations. Our method requires minimal assumptions about the system, and is applicable even to un-aligned polyatomic molecules.
Alexander O, Barillot T, Cooper B, et al., 2021, Inner Valence Hole Migration in Isopropanol, Conference on Lasers and Electro-Optics Europe / European Quantum Electronics Conference (CLEO/Europe-EQEC), Publisher: IEEE
Driver T, Cooper B, Ayers R, et al., 2020, Two-dimensional partial covariance mass spectrometry of large molecules based on fragment correlations, Physical Review X, Vol: 10, Pages: 041004 – 1-041004 – 13, ISSN: 2160-3308
Covariance mapping [L. J. Frasinski, K. Codling, and P. A. Hatherly, Science 246, 1029 (1989)] is a well-established technique used for the study of mechanisms of laser-induced molecular ionization and decomposition. It measures statistical correlations between fluctuating signals of pairs of detected species (ions, fragments, electrons). A positive correlation identifies pairs of products originating from the same dissociation or ionization event. A major challenge for covariance-mapping spectroscopy is accessing decompositions of large polyatomic molecules, where true physical correlations are overwhelmed by spurious signals of no physical significance induced by fluctuations in experimental parameters. As a result, successful applications of covariance mapping have so far been restricted to low-mass systems, e.g., organic molecules of around 50 daltons (Da). Partial-covariance mapping was suggested to tackle the problem of spurious correlations by taking into account the independently measured fluctuations in the experimental conditions. However, its potential has never been realized for the decomposition of large molecules, because in these complex situations, determining and continuously monitoring multiple experimental parameters affecting all the measured signals simultaneously becomes unfeasible. We introduce, through deriving theoretically and confirming experimentally, a conceptually new type of partial-covariance mapping—self-correcting partial-covariance spectroscopy—based on a parameter extracted from the measured spectrum itself. We use the readily available total ion count as the self-correcting partial-covariance parameter, thus eliminating the challenge of determining experimental parameter fluctuations in covariance measurements of large complex systems. The introduced self-correcting partial covariance enables us to successfully resolve correlations of molecules as large as
O'Neal JT, Champenois EG, Oberli S, et al., 2020, Electronic Population Transfer via Impulsive Stimulated X-Ray Raman Scattering with Attosecond Soft-X-Ray Pulses, PHYSICAL REVIEW LETTERS, Vol: 125, ISSN: 0031-9007
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- Citations: 25
Weaver B, Greening D, Tisch J, et al., 2020, Generation and measurement of isolated attosecond pulses with enhanced flux using a two colour synthesized laser field, Optics Express, Vol: 28, Pages: 23329-23337, ISSN: 1094-4087
We have generated isolated attosecond pulses and performed attosecond streaking measurements using a two-colour synthesized laser field consisting of a strong near-infrared few-cycle pulse and a weaker multi-cycle pulse centred at 400 nm. An actively stabilized interferometer was used to coherently combine the two pulses. Using attosecond streaking we characterised the electric fields of the two pulses and accurately retrieved the spectrum of the multi-cycle pulse. We demonstrated a two-fold increase in the flux of isolated attosecond pulses produced and show that their duration was minimally affected by the presence of the weaker field due to spectral filtering by a multilayer mirror.
Marangos JP, 2020, Accessing the quantum spatial and temporal scales with XFELs, Nature Reviews Physics, Vol: 2, Pages: 332-334, ISSN: 2522-5820
X-ray free-electron lasers (XFELs) are unique tools that are making possible time-resolved measurements of structural and electronic dynamics at the quantum spatial and temporal scales. Jonathan Marangos discusses the transformative scientific potential of this capability but also stresses the importance of lowering barriers to access to maximize scientific reach.
Johnson AS, Austin DR, Wood DA, et al., 2020, High-flux soft x-ray harmonic generation from ionization-shaped few-cycle laser pulses (vol 4, eaar3761, 2018), SCIENCE ADVANCES, Vol: 6, ISSN: 2375-2548
Longetti L, Randulova M, Ojeda J, et al., 2020, Photoemission from non-polar aromatic molecules in the gas and liquid phase, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, Vol: 22, Pages: 3965-3974, ISSN: 1463-9076
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- Citations: 4
Driver T, Li S, Champenois EG, et al., 2020, Attosecond transient absorption spooktroscopy: a ghost imaging approach to ultrafast absorption spectroscopy, Physical Chemistry Chemical Physics, Vol: 22, Pages: 2704-2712, ISSN: 1463-9076
The recent demonstration of isolated attosecond pulses from an X-ray free-electron laser (XFEL) opens the possibility for probing ultrafast electron dynamics at X-ray wavelengths. An established experimental method for probing ultrafast dynamics is X-ray transient absorption spectroscopy, where the X-ray absorption spectrum is measured by scanning the central photon energy and recording the resultant photoproducts. The spectral bandwidth inherent to attosecond pulses is wide compared to the resonant features typically probed, which generally precludes the application of this technique in the attosecond regime. In this paper we propose and demonstrate a new technique to conduct transient absorption spectroscopy with broad bandwidth attosecond pulses with the aid of ghost imaging, recovering sub-bandwidth resolution in photoproduct-based absorption measurements.
Duris J, Li S, Driver T, et al., 2020, Tunable isolated attosecond x-ray pulses with Gigawatt peak power from a free-electron laser, Nature Photonics, Vol: 14, Pages: 30-36, ISSN: 1749-4885
The quantum mechanical motion of electrons in molecules and solids occurs on the sub-femtosecond timescale. Consequently, the study of ultrafast electronic phenomena requires thegeneration of laser pulses shorter than 1 fs and of sufficient intensity to interact with their targetwith high probability. Probing these dynamics with atomic-site specificity requires the extensionof sub-femtosecond pulses to the soft X-ray spectral region. Here we report the generation of iso-lated soft X-ray attosecond pulses with an X-ray free-electron laser. Our source has a pulse energythat is a million times larger than any other source of isolated attosecond pulses in the soft X-rayspectral region, with a peak power exceeding 100 GW. This unique combination of high intensity,high photon energy and short pulse duration enables the investigation of electron dynamics withX-ray non-linear spectroscopy and single-particle imaging, unlocking a path towards a new era ofattosecond science.
Pettipher AJ, Weaver B, Greening D, et al., 2020, Optimisation of a Femtosecond Pulse Synthesiser for High Harmonic Generation Using the Semi-Classical Model, Conference on Lasers and Electro-Optics (CLEO), Publisher: IEEE, ISSN: 2160-9020
Berrah N, Sanchez-Gonzalez A, Jurek Z, et al., 2019, Femtosecond-resolved observation of the fragmentation of buckminsterfullerene following X-ray multiphoton ionization (vol 15, pg 1279, 2019), NATURE PHYSICS, Vol: 15, Pages: 1301-1301, ISSN: 1745-2473
Berrah N, Sanchez-Gonzalez A, Jurek Z, et al., 2019, Femtosecond-resolved observation of the fragmentation of buckminsterfullerene following X-ray multiphoton ionization, Nature Physics, Vol: 15, Pages: 1279-1283, ISSN: 1745-2473
X-ray free-electron lasers have, over the past decade, opened up the possibility of understanding the ultrafast response of matter to intense X-ray pulses. In earlier research on atoms and small molecules, new aspects of this response were uncovered, such as rapid sequences of inner-shell photoionization and Auger ionization. Here, we studied a larger molecule, buckminsterfullerene (C60), exposed to 640 eV X-rays, and examined the role of chemical effects, such as chemical bonds and charge transfer, on the fragmentation following multiple ionization of the molecule. To provide time resolution, we performed femtosecond-resolved X-ray pump/X-ray probe measurements, which were accompanied by advanced simulations. The simulations and experiment reveal that despite substantial ionization induced by the ultrashort (20 fs) X-ray pump pulse, the fragmentation of C60 is considerably delayed. This work uncovers the persistence of the molecular structure of C60, which hinders fragmentation over a timescale of hundreds of femtoseconds. Furthermore, we demonstrate that a substantial fraction of the ejected fragments are neutral carbon atoms. These findings provide insights into X-ray free-electron laser-induced radiation damage in large molecules, including biomolecules.
Johnson AS, Avni T, Larsen E, et al., 2019, Attosecond soft X-ray high harmonic generation, PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES, Vol: 377, ISSN: 1364-503X
Marangos JP, 2019, The measurement of ultrafast electronic and structural dynamics with X-rays, PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES, Vol: 377, ISSN: 1364-503X
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