A5015427831- Mass Spectrometry Techniques and Applications
- Laser-Matter Interactions and Applications
- Atomic and Molecular Physics
- Advanced Chemical Physics Studies
- Ion-surface interactions and analysis
- Spectroscopy and Laser Applications
- Laser-induced spectroscopy and plasma
- Astrophysics and Star Formation Studies
- Atomic and Subatomic Physics Research
- Advanced Physical and Chemical Molecular Interactions
- Nuclear Physics and Applications
- Laser Design and Applications
- Analytical chemistry methods development
- Advanced X-ray Imaging Techniques
- Radiation Detection and Scintillator Technologies
- X-ray Spectroscopy and Fluorescence Analysis
- Diamond and Carbon-based Materials Research
- Electron and X-Ray Spectroscopy Techniques
- Atmospheric Ozone and Climate
- High-pressure geophysics and materials
- Quantum, superfluid, helium dynamics
- Microfluidic and Capillary Electrophoresis Applications
- Water Quality Monitoring and Analysis
- Laser-Plasma Interactions and Diagnostics
- Isotope Analysis in Ecology
University of Oxford
2014-2024
Deutsches Elektronen-Synchrotron DESY
2020-2024
Oxfam
2014-2019
Aarhus University
2018
University of California, Berkeley
2018
University of Connecticut
2018
Lund University
2018
Max-Born-Institute for Nonlinear Optics and Short Pulse Spectroscopy
2018
Helmholtz-Zentrum Dresden-Rossendorf
2018
Kansas State University
2018
Abstract Polycyclic aromatic hydrocarbons (PAHs) play an important role in interstellar chemistry and are subject to high energy photons that can induce excitation, ionization, fragmentation. Previous studies have demonstrated electronic relaxation of parent PAH monocations over 10–100 femtoseconds as a result beyond-Born-Oppenheimer coupling between the nuclear dynamics. Here, we investigate three molecules: fluorene, phenanthrene, pyrene, using ultrafast XUV IR laser pulses. Simultaneous...
The development of sensors capable detecting particles and radiation with both high time positional resolution is key to improving our understanding in many areas science. Example applications such range from fundamental scattering studies chemical reaction mechanisms through imaging mass spectrometry surfaces, neutron aimed at probing the structure materials, time-resolved fluorescence measurements elucidate function biomolecules. In addition improved throughput resulting parallelisation...
The cold neutron imaging and diffraction instrument IMAT at the second target station of pulsed source ISIS is currently being commissioned prepared for user operation. will enable white-beam radiography tomography. One benefits operating on a to determine energy via time flight measurement, thus enabling energy-selective energy-dispersive imaging, maximizing image contrasts between given materials mapping structure microstructure properties. We survey hardware software components data...
The dynamics following laser-induced molecular photodissociation of gas-phase ${\mathrm{CH}}_{2}\mathrm{BrI}$ at 271.6 nm were investigated by time-resolved Coulomb-explosion imaging using intense near-IR femtosecond laser pulses. observed delay-dependent photofragment momenta reveal that undergoes C-I cleavage, depositing 65.6% the available energy into internal product states, and absorption a second UV photon breaks C-Br bond ${\mathrm{CH}}_{2}\mathrm{Br}$. Simulations confirm this...
The photodissociation dynamics of CH3I and CH2ClI at 272 nm were investigated by time-resolved Coulomb explosion imaging, with an intense non-resonant 815 probe pulse. Fragment ion momenta over a wide m/z range recorded simultaneously coupling velocity map imaging spectrometer pixel mass spectrometry camera. For both molecules, delay-dependent pump-probe features assigned to ultraviolet-induced carbon-iodine bond cleavage followed explosion. Multi-mass also allowed the sequential...
Due to its element- and site-specificity, inner-shell photoelectron spectroscopy is a widely used technique probe the chemical structure of matter. Here we show that time-resolved can be employed observe ultrafast reactions electronic response nuclear motion with high sensitivity. The ultraviolet dissociation iodomethane (CH$_3$I) investigated by ionization above iodine 4d edge, using photoion spectroscopy. dynamics observed in spectra appear earlier are faster than those seen fragments....
We explore time-resolved Coulomb explosion induced by intense, extreme ultraviolet (XUV) femtosecond pulses from the FLASH free-electron laser as a method to image photo-induced molecular dynamics in two molecules, iodomethane and 2,6-difluoroiodobenzene. At an excitation wavelength of 267\,nm, dominant reaction pathway both molecules is neutral dissociation via cleavage carbon--iodine bond. This allows investigating influence environment on absorption XUV pulse subsequent process. find that...
We present the first multimass velocity-map imaging data acquired using a new ultrafast camera designed for time-resolved particle imaging. The PImMS (Pixel Imaging Mass Spectrometry) sensor allows events to be imaged with time resolution as high 25 ns over acquisition times of more than 100 μs. In photofragment studies, this images multiple fragment masses on each time-of-flight cycle. describe architecture and bench-testing photofragments formed in UV photolysis two test molecules: Br2...
Absolute gas-phase electron ionization cross-sections have been measured for functional group analogues of the nucleobase and sugar backbone constituents DNA RNA.
The gas-phase structures of four difluoroiodobenzene and two dihydroxybromobenzene isomers were identified by correlating the emission angles atomic fragment ions created following femtosecond laser-induced Coulomb explosion. structural determinations facilitated confining most polarizable axis each molecule to detection plane prior explosion event using one-dimensional adiabatic alignment. For a molecular target consisting isomers, constituent structure could additionally be singled out...
Naphthalene and azulene are isomeric polycyclic aromatic hydrocarbons (PAHs) topical in the context of astrochemistry due to recent discovery substituted naphthalenes Taurus Molecular Cloud-1 (TMC-1). Here, thermal- photo-induced isomerization, dissociation, radiative cooling dynamics energized (vibrationally hot) naphthalene (Np+) (Az+) radical cations, occurring over microsecond seconds timescale, investigated using a cryogenic electrostatic ion storage ring, affording “molecular cloud...
Atmospheric aerosol particles are important in many atmospheric processes such as: light scattering, absorption, and cloud formation. Oxidation reactions continuously change the chemical composition of particles, especially organic mass component, which is often dominant fraction. These ageing poorly understood but known to significantly affect formation potential particles. In this study we investigate effect humidity ozone on two model systems: oleic acid arachidonic acid. acids also...
Over the past decade or so, state-of-the-art in field of chemical reaction dynamics has progressed from studies few-atom systems to wide-ranging investigations into a variety photoinduced and collision-induced processes much larger molecules. Many these are direct relevance wide audience chemists, spanning fields such as atmospheric chemistry, astrochemistry, synthetic biology. Key this work been technique velocity-map imaging, which allows complete product scattering distributions be...
We present results from an experimental ion imaging study into the fragmentation dynamics of 1-iodopropane and 2-iodopropane following interaction with extreme ultraviolet intense femtosecond laser pulses a photon energy 95 eV. Using covariance analysis, range observed pathways resulting polycations can be isolated interrogated in detail at relatively high count rates (∼12 ions shot-1). By incorporating recently developed native frames analysis approach three-dimensional procedure,...
Inner-shell photoelectron spectroscopy provides an element-specific probe of molecular structure, as core-electron binding energies are sensitive to the chemical environment. Short-wavelength femtosecond light sources, such Free-Electron Lasers (FELs), even enable time-resolved site-specific investigations photochemistry. Here, we study ultraviolet photodissociation prototypical chiral molecule 1-iodo-2-methylbutane, probed by extreme-ultraviolet (XUV) pulses from Free-electron LASer in...
Recent developments in X-ray free-electron lasers have enabled a novel site-selective probe of coupled nuclear and electronic dynamics photoexcited molecules, time-resolved photoelectron spectroscopy (TRXPS). We present results from joint experimental theoretical TRXPS study the well-characterized ultraviolet photodissociation CS2, prototypical system for understanding non-adiabatic dynamics. These demonstrate that sulfur 2p binding energy is sensitive to changes structure following...
Abstract Structural imaging of transient excited-state species is a key goal molecular physics, promising to unveil rich information about the dynamics underpinning photochemical transformations. However, separating electronic and nuclear contributions spectroscopic observables challenging, typically requires application high-level theory. Here, we employ site-selective ionisation via ultrashort soft X-ray pulses time-resolved Coulomb explosion interrogate structural ultraviolet...
Laser-induced adiabatic alignment and mixed-field orientation of 2,6-difluoroiodobenzene (C6H3F2I) molecules are probed by Coulomb explosion imaging following either near-infrared strong-field ionization or extreme-ultraviolet multi-photon inner-shell using free-electron laser pulses. The resulting photoelectrons fragment ions captured a double-sided velocity map spectrometer projected onto two position-sensitive detectors. ion side the is equipped with pixel mass spectrometry camera,...
Ultrafast laser pump-probe methods allow chemical reactions to be followed in real time, and have provided unprecedented insight into fundamental aspects of reactivity. While evolution the electronic structure system under study is evident from changes observed spectral signatures, information on rearrangement nuclear framework generally obtained indirectly. Disentangling contributions signal arising competing photochemical pathways can also challenging. Here we introduce new technique...
Laser-induced Coulomb explosions can be used to identify gas-phase molecular structures through correlations between fragment ion trajectories. This report presents a model for predicting these outcomes, which first establishes the neutral equilibrium geometry of target molecule using electronic structure calculations, and then samples probability distribution potential ground-state configurations by allowing zero-point vibrational motion. Candidate are assumed explode instantaneously into...
This paper reports a crossed-beam velocity-map imaging study into the electron ionization dynamics of jet-cooled ${\mathrm{N}}_{2}$ and ${\mathrm{O}}_{2}$ molecules at collision energies from 35 to 100 eV. The use detection provides insight detailed through dimension product ion kinetic energy associated with impulsive dissociation. In particular, ``mesoscopic'' cross sections corresponding manifolds energetically close states converging same dissociation asymptote are reported for number...
The Pixel-Imaging Mass Spectrometry (PImMS) camera allows for 3D charged particle imaging measurements, in which the time-of-flight is recorded along with (x, y) position. Coupling PImMS to an ultrafast pump-probe velocity-map spectroscopy apparatus therefore provides a route time-resolved multi-mass ion imaging, both high count rates and large dynamic range, thus allowing rapid measurements of complex photofragmentation dynamics. Furthermore, use vacuum ultraviolet wavelengths probe pulse...
The predissociation dynamics of the 6s (B2E) Rydberg state gas-phase CH3I were investigated by time-resolved Coulomb-explosion imaging using extreme ultraviolet (XUV) free-electron laser pulses. Inner-shell ionization at iodine 4d edge was utilized to provide a site-specific probe ensuing dynamics. combination velocity-map (VMI) spectrometer coupled with pixel mass spectrometry (PImMS) camera permitted three-dimensional ionic fragment momenta be recorded simultaneously for wide range charge...