A5020223690- Advanced Chemical Physics Studies
- Spectroscopy and Laser Applications
- Mass Spectrometry Techniques and Applications
- Atmospheric Ozone and Climate
- Spectroscopy and Quantum Chemical Studies
- Laser-Matter Interactions and Applications
- Ion-surface interactions and analysis
- Cold Atom Physics and Bose-Einstein Condensates
- Atomic and Molecular Physics
- Atmospheric chemistry and aerosols
- Atomic and Subatomic Physics Research
- Quantum, superfluid, helium dynamics
- Photochemistry and Electron Transfer Studies
- Nuclear Physics and Applications
- Radiation Detection and Scintillator Technologies
- Various Chemistry Research Topics
- Molecular spectroscopy and chirality
- Laser-induced spectroscopy and plasma
- Particle Detector Development and Performance
- Molecular Junctions and Nanostructures
- CCD and CMOS Imaging Sensors
- Molecular Spectroscopy and Structure
- Quantum optics and atomic interactions
- Laser-Plasma Interactions and Diagnostics
- Inorganic Fluorides and Related Compounds
University of Oxford
2015-2024
University of Maryland, College Park
2007-2020
Science Oxford
2015-2020
Oxfam
2014-2020
Universidad de Salamanca
2019
Aarhus University
2015-2018
University of California, Berkeley
2018
University of Connecticut
2018
Lund University
2018
Max-Born-Institute for Nonlinear Optics and Short Pulse Spectroscopy
2018
This paper concerns the semiclassical description, calculation and measurement of angular momentum polarization in products elementary gas-phase bimolecular reactions. A unified, treatment centre-of-mass correlated (k,k′,j′) distribution involving reagent product relative velocity vectors is described, related to other methodologies already existing literature. Explicit expressions are provided enabling experimentalists extract rotational information from crossed-molecular beam...
The torsional motion of a molecule composed two substituted benzene rings, linked by single bond, is coherently controlled pair strong ($3\ifmmode\times\else\texttimes\fi{}1{0}^{13}\text{ }\text{ }\mathrm{W}\text{ }{\mathrm{cm}}^{\ensuremath{-}2}$), nonresonant (800 nm) 200-fs-long laser pulses---both linearly polarized perpendicular to the single-bond axis. If second pulse sent at time when rings rotate toward (away from) each other amplitude torsion strongly enhanced (reduced). persists...
The ``pixel imaging mass spectrometry'' camera is used to perform femtosecond laser-induced Coulomb explosion of 3,5-dibromo-3${}^{\ensuremath{'}}$,5${}^{\ensuremath{'}}$-difluoro-4${}^{\ensuremath{'}}$-cyanobiphenyl molecules prealigned in space. experiment allows the concurrent detection correlated two-dimensional momentum images all ionic fragments resulting from fragmentation multiple each acquisition cycle. studies provide rich information about parent molecular structure and dynamics,...
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...
We extend covariance velocity map ion imaging to four particles, establishing cumulant mapping and allowing for measurements that provide insights usually associated with coincidence detection, but at much higher count rates. Without correction, a fourfold analysis is contaminated by the pairwise correlations of uncorrelated events, we have addressed this calculation full cumulant, which subtracts correlations. demonstrate approach on four-body breakup formaldehyde following strong field...
The detailed stereodynamics of the H+CO2 system have been studied using polarized Doppler resolved laser induced fluorescence to state selectively probe OH product. lambda-doublet specific differential cross-sections and translational energy distributions were measured, along with scattering angle dependence rotational angular momentum polarization. observed centre-of-mass cross-section has significant contributions in both forward backward hemispheres, a small preference for scattering,...
Velocity-aligned, superthermal O(1D) atoms generated via the photodissociation of N2O have been employed to investigate stereodynamics title reaction. The power this experimental technique, when coupled with Doppler-resolved, polarized laser-induced fluorescence probing reaction products, is demonstrated by reference specific channel leading NO(υ′=0)+NO(υ′=16,17), which shown proceed direct stripping dynamics. Furthermore, observed product-state selective linear and angular momenta disposals...
PImMS, or Pixel Imaging Mass Spectrometry, is a novel high-speed monolithic CMOS imaging sensor tailored to mass spectrometry requirements, also suitable for other dark-field applications. In its application time-of-flight spectrometry, the permits ion arrival time distributions be combined with 2D imaging, providing additional information about initial position velocity of ions under study. PImMS1, first generation in this family, comprises an array 72 by pixels on 70 μm pitch. Pixels...
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...
Femtosecond laser-induced Coulomb-explosion imaging of 3,5-dibromo-$3{}^{\ensuremath{'}},5{}^{\ensuremath{'}}$-difluoro-$4{}^{\ensuremath{'}}$-cyanobiphenyl molecules prealigned in space is explored using a pixel-imaging mass-spectrometry (PImMS) camera. The fast-event-triggered camera allows the concurrent detection correlated two-dimensional momentum images, or covariance maps, all ionic fragments resulting from fragmentation multiple each acquisition cycle. Detailed simulation maps...
New measurements of the differential steric effect for NO + Ar inelastic scattering highlight importance quantum interference.
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...
Rigorous quantum dynamical calculations have been performed on the ground $1^{1}A^{\ensuremath{'}}$ and first excited $1^{1}A^{\ensuremath{'}\ensuremath{'}}$ electronic states of title reaction, employing most accurate potential energy surfaces available. Product rovibrational state populations rotational angular momentum alignment parameters are reported, compared with new experimental, quasiclassical trajectory calculated results. The agree quantitatively experiment, reveal unequivocally...
This paper, which is the companion to experimental paper (M. Brouard, S. P. Duxon, A. Enriquez and J. Simons, Chem. Soc., Faraday Trans., 1993, 89, 1435) in this issue, divided into two parts. In first, equations for laboratory (LAB) velocity distribution of products generated via photoionitiated bimolecular reaction are presented. These provide basis numerical simulation these distributions from assumed forms centre-of-mass (CM) differential cross-section: results may be compared directly...
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTExperimental and RRKM modeling study of the methyl + hydrogen atom deuterium reactionsMark Brouard, Martyn T. Macpherson, Michael J. PillingCite this: Phys. Chem. 1989, 93, 10, 4047–4059Publication Date (Print):May 1, 1989Publication History Published online1 May 2002Published inissue 1 1989https://pubs.acs.org/doi/10.1021/j100347a037https://doi.org/10.1021/j100347a037research-articleACS PublicationsRequest reuse permissionsArticle...
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTObservation of equilibration in the system atomic hydrogen + ethylene .dblharw. ethyl. The determination heat formation ethyl radicalMark Brouard, Phillip D. Lightfoot, and Michael J. PillingCite this: Phys. Chem. 1986, 90, 3, 445–450Publication Date (Print):January 1, 1986Publication History Published online1 May 2002Published inissue 1 January 1986https://pubs.acs.org/doi/10.1021/j100275a019https://doi.org/10.1021/j100275a019research-articleACS...
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...
Rotational angular momentum alignment effects in the rotationally inelastic collisions of NO(X) with Ar have been investigated at a collision energy 66 meV by means hexapole electric field initial state selection coupled velocity-map ion imaging final detection. The fully quantum resolved second rank renormalized polarization dependent differential cross sections determined experimentally are reported for spin-orbit conserving and changing transitions first time. results compared findings...
Introduction Potential energy surfaces: the forces of chemistry Scattering theory: predicting outcome chemical events Processes involving multiple potential surfaces Inelastic scattering: transfer in collisions Reactive reactions three dimensions quantum state-resolved Photodissociation dynamics: fragmentation molecules by light Stereodynamics: role orientation and alignment Surface molecular at interfaces Femtochemistry control reactivity Cold collisions: ultra low temperatures Study boxes