A5058434713- Advanced Chemical Physics Studies
- Atomic and Molecular Physics
- Mass Spectrometry Techniques and Applications
- X-ray Spectroscopy and Fluorescence Analysis
- Photochemistry and Electron Transfer Studies
- Electron and X-Ray Spectroscopy Techniques
- Spectroscopy and Quantum Chemical Studies
- Spectroscopy and Laser Applications
- Atmospheric Ozone and Climate
- Inorganic Fluorides and Related Compounds
- Atmospheric chemistry and aerosols
- Laser-Matter Interactions and Applications
- Molecular Junctions and Nanostructures
- Advanced X-ray Imaging Techniques
- Photocathodes and Microchannel Plates
- Luminescence Properties of Advanced Materials
- Ion-surface interactions and analysis
- Quantum, superfluid, helium dynamics
- Catalytic Processes in Materials Science
- Analytical chemistry methods development
- Particle Accelerators and Free-Electron Lasers
- Chemical Thermodynamics and Molecular Structure
- Nuclear Physics and Applications
- Laser-Plasma Interactions and Diagnostics
- Laser Design and Applications
Daresbury Laboratory
2016-2025
Sci-Tech Daresbury
2014-2024
University of Nottingham
2017
Cockcroft Institute
2013-2014
University of Ottawa
2006-2010
Heriot-Watt University
2009-2010
Cardiff University
2009-2010
Lomonosov Moscow State University
2010
CalGavin (United Kingdom)
1996-1998
Thomson Foundation
1980-1989
A comparison of the electronic structure rutile (110), anatase (101), and (001) single-crystal surfaces has been made using resonant photoemission x-ray absorption spectroscopy. Under identical preparative conditions, (101) surface shows lowest $\mathrm{Ti}\phantom{\rule{0.3em}{0ex}}3d$ $4sp$ hybridization in states close to valence-band maximum three surfaces. It also highest concentration surface-oxygen vacancies. The effect on modifying route thus vacancies is examined....
A time-of-flight spectrometer has been coupled with a source of synchrotron radiation to measure the photoionisation cross sections for multiple ionisation rare gases He Xe in photon energy range 50-280 eV. Comparison is made theoretical calculations both case double He, Ne and Ar single Kr Xe, where electron correlation effects are supposed enhance various sections. The importance an accurate knowledge monochromator scattered light such experiments emphasised.
Abstract The light-induced ultrafast switching between molecular isomers norbornadiene and quadricyclane can reversibly store release a substantial amount of chemical energy. Prior work observed signatures dynamics in both upon ultraviolet excitation but could not follow the electronic relaxation all way back to ground state experimentally. Here we study after exciting (201 nanometres) using time-resolved gas-phase extreme photoelectron spectroscopy combined with non-adiabatic simulations....
Identifying multiple rival reaction products and transient species formed during ultrafast photochemical reactions determining their time-evolving relative populations are key steps toward understanding predicting outcomes. Yet, most contemporary studies struggle with clearly identifying quantifying competing molecular structures/species among the emerging products. Here, we show that mega-electronvolt electron diffraction in combination ab initio dynamics calculations offer a powerful route...
The complete valence shell photoelectron spectra of cytosine, thymine and adenine have been investigated experimentally theoretically. Vertical ionization energies spectral intensities evaluated using the many-body Green's function method, thereby enabling theoretical to be derived. In influence tautomers rotational conformers has investigated. calculated display a satisfactory agreement with experimental data this allowed most bands assigned. Photoelectron asymmetry parameters determined...
Ultrafast time-resolved photoelectron spectra are reported for the vacuum-ultraviolet (VUV) photoionization of acetylene following excitation to Ã1Au state via UV absorption at 200 nm. The energy lies above lowest dissociation threshold C2H X̃2Σ+ + H, as well adiabatic form (Ã2Π) H. time-dependent mass and provide insight into intramolecular decay processes state. In addition, with VUV light access both X̃2Πu Ã2Σg+ states ion, predicted, but previously unobserved, 1 2Πg state, which...
We report the first study of UV-induced photoisomerization probed via core ionization by an x-ray laser. investigated and fragmentation cyclohexadiene-hexatriene system at 850 eV during ring opening. find that ion-fragmentation patterns evolve over a picosecond, reflecting change in state excitation molecular geometry: average kinetic energy per ion fragment H+-ion count increase as opens molecule elongates. discuss new opportunities for photophysics created optical pump probe...
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....
The absolute photoabsorption, photoionization and photodissociation cross sections the quantum efficiency of ammonia deuterated have been measured from ionization threshold to 25 eV using a double ion chamber monochromated synchrotron radiation. photoabsorption spectrum displays extensive vibrational progressions associated with Rydberg series converging onto excited levels 2A2´´ state. New structure has observed for ND3 in 10.0-11.3 range, due transitions into , states recorded improved...
The valence shell photoelectron spectrum of purine has been studied experimentally and theoretically. Synchrotron radiation used to record spectra at photon energies 45 85 eV. Photoelectron angular distributions have determined these provide an experimental means distinguishing between σ-and π-type orbitals. Vertical ionization spectral intensities evaluated using the many-body Green function method. calculated agree well with results in outer region proved be indispensable for interpreting...
Vibrational branching ratios and photoelectron angular distributions for alternative vibrational levels of C2H2+X 2Πu have been measured in the range 13 eV⩽hν⩽25 eV using synchrotron radiation. Below hν∼16 eV, these data exhibit strong non-Franck–Condon effects, namely, wavelength-dependent vibrational-state-dependent asymmetry parameters. Moreover, enhanced excitation bending modes ion is observed below addition to C–C stretch mode, which only mode readily spectra C2H2 at shorter...
The valence shell electronic states of pyrimidine and pyrazine have been studied experimentally theoretically. absolute photoabsorption cross sections measured between 4 40 eV, using synchrotron radiation, are dominated by prominent bands associated with intravalence transitions. In contrast, the structure due to Rydberg excitations is weak, but series observed converging onto or limits in pyrazine. A comparison spectrum pyrazine-h4 that for pyrazine-d4, together calculated transition...
Multiple photoionization of neon atoms by a strong 13.7 nm (90.5 eV) laser pulse has been studied at the FLASH free electron in Hamburg. A velocity map imaging spectrometer was used to record angle-resolved photoelectron spectra on single-shot basis. Analysis evolution with FEL energy combination extensive theoretical calculations allows ionization pathways that contribute be assigned, revealing occurrence sequential three-photon triple ionization.