Andrew J. Orr‐Ewing
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View article: Global modeling of trifluoroacetic acid surface concentration and deposition from the gas-phase oxidation of a wide range of precursor hydrofluoroolefins
Global modeling of trifluoroacetic acid surface concentration and deposition from the gas-phase oxidation of a wide range of precursor hydrofluoroolefins Open
Oxidation of hydrofluoroolefins (HFOs) is a source of trifluoroacetic acid (TFA) in the lower atmosphere.
View article: Atmospheric Oxidation of Hydrofluoroolefins and Hydrochlorofluoroolefins by Ozone Produces HFC-23, PFC-14, and CFC-13
Atmospheric Oxidation of Hydrofluoroolefins and Hydrochlorofluoroolefins by Ozone Produces HFC-23, PFC-14, and CFC-13 Open
Hydrofluoroolefins (HFOs) and hydrochlorofluoroolefins (HCFOs) are fluorinated compounds developed to replace refrigerant and propellant gases known to be ozone-depleting substances and/or potent greenhouse gases (GHGs). Their short atmosp…
View article: Ultrafast Excited-State Dynamics of the Organic Photoredox Catalyst DDQ
Ultrafast Excited-State Dynamics of the Organic Photoredox Catalyst DDQ Open
The electron-deficient oxidant 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) has recently emerged as a promising visible-light photoredox catalyst. However, its excited-state behavior remains poorly understood. Here, we investigate the u…
View article: Dynamic Equilibrium between the Fluorescent State of Tryptophan and Its Cation-Electron Ion Pair Governs Triplet State Population
Dynamic Equilibrium between the Fluorescent State of Tryptophan and Its Cation-Electron Ion Pair Governs Triplet State Population Open
Tryptophan is the most efficient fluorophore of the naturally occurring amino acids and is widely used as a fluorescence probe of protein structure and function. As a result of its importance, there have been numerous studies of the ultraf…
View article: Solvent-Dependent Ultrafast Photochemical Dynamics of <i>N</i>-Methyl Oxindole Overcrowded Alkene Molecular Motors
Solvent-Dependent Ultrafast Photochemical Dynamics of <i>N</i>-Methyl Oxindole Overcrowded Alkene Molecular Motors Open
Overcrowded alkenes are a class of rotational molecular motors that operate via alternating photochemical and thermal relaxation processes. Although the performances of various designs of molecular motors have been extensively studied, in …
View article: Imaging the Photochemistry of Cyclobutanone using Ultrafast Electron Diffraction: Experimental Results
Imaging the Photochemistry of Cyclobutanone using Ultrafast Electron Diffraction: Experimental Results Open
We investigated the ultrafast structural dynamics of cyclobutanone following photoexcitation at $λ=200$ nm using gas-phase megaelectronvolt ultrafast electron diffraction. Our investigation complements the simulation studies of the same pr…
View article: Oxidative benzylic C(sp <sup>3</sup> )–H functionalisation of electron-poor substrates with photoexcited DDQ
Oxidative benzylic C(sp <sup>3</sup> )–H functionalisation of electron-poor substrates with photoexcited DDQ Open
Photochemical excitation of DDQ enables oxidative functionalisation of otherwise inaccessible electron-poor benzylic C(sp 3 )–H bonds, affording quinol ethers via a single electron transfer pathway.
View article: Exchange, promiscuity, and orthogonality in <i>de novo</i> designed coiled-coil peptide assemblies
Exchange, promiscuity, and orthogonality in <i>de novo</i> designed coiled-coil peptide assemblies Open
Dynamics and exchange between coiled-coil assemblies are evaluated by a fluorescence-based assay. De novo designed homo-dimers to heptamers are tested for faithful and promiscuous interactions, and re-designed to deliver an orthogonal set.
View article: Wavelength- and pH-Dependent Optical Properties of Aqueous Aerosol Particles Containing 4-Nitrocatechol
Wavelength- and pH-Dependent Optical Properties of Aqueous Aerosol Particles Containing 4-Nitrocatechol Open
The radiative forcing caused by atmospheric aerosol represents one of the largest uncertainties in climate models. In part, these uncertainties derive from poor characterizations of the optical properties of light-absorbing brown carbon (B…
View article: Efficient Ground-State Recovery of UV-Photoexcited <i>p</i>-Nitrophenol in Aqueous Solution by Direct and Multistep Pathways
Efficient Ground-State Recovery of UV-Photoexcited <i>p</i>-Nitrophenol in Aqueous Solution by Direct and Multistep Pathways Open
Nitroaromatic compounds are found in brown carbon aerosols emitted to the Earth's atmosphere by biomass burning, and are important organic chromophores for the absorption of solar radiation. Here, transient absorption spectroscopy spanning…
View article: Exchange, promiscuity, and orthogonality in<i>de novo</i>designed coiled-coil peptide assemblies
Exchange, promiscuity, and orthogonality in<i>de novo</i>designed coiled-coil peptide assemblies Open
De novo protein design is delivering new peptide and protein structures at a rapid pace. Many of these synthetic polypeptides form well-defined and hyperthermal-stable structures. Generally, however, less is known about the dynamic propert…
View article: Competing Nonadiabatic Relaxation Pathways for Near-UV Excited <i>ortho</i>-Nitrophenol in Aqueous Solution
Competing Nonadiabatic Relaxation Pathways for Near-UV Excited <i>ortho</i>-Nitrophenol in Aqueous Solution Open
Nitrophenols are atmospheric pollutants found in brown carbon aerosols produced by biomass burning. Absorption of solar radiation by these nitrophenols contributes to atmospheric radiative forcing, but quantifying this climate impact requi…
View article: Perspective on Theoretical and Experimental Advances in Atmospheric Photochemistry
Perspective on Theoretical and Experimental Advances in Atmospheric Photochemistry Open
Research that explores the chemistry of Earth's atmosphere is central to the current understanding of global challenges such as climate change, stratospheric ozone depletion, and poor air quality in urban areas. This research is a synergis…
View article: Femtosecond to Microsecond Observation of Photochemical Pathways in Nitroaromatic Phototriggers Using Transient Absorption Spectroscopy
Femtosecond to Microsecond Observation of Photochemical Pathways in Nitroaromatic Phototriggers Using Transient Absorption Spectroscopy Open
The synthetic accessibility and tolerance to structural modification of phototriggered compounds (PTs) based on the ortho- nitrobenzene (ONB) protecting group have encouraged a myriad of applications including optimization of biological ac…
View article: The Role of Momentum Partitioning in Covariance Ion Imaging Analysis
The Role of Momentum Partitioning in Covariance Ion Imaging Analysis Open
We present results from a covariance ion imaging study, which employs extensive filtering, on the relationship between fragment momenta to gain deeper insight into photofragmentation dynamics. A new data analysis approach is introduced tha…
View article: Collection on the Spectroscopy, Structure, and Reactivity of Stabilized Criegee Intermediates
Collection on the Spectroscopy, Structure, and Reactivity of Stabilized Criegee Intermediates Open
ADVERTISEMENT RETURN TO ISSUEEditorialNEXTCollection on the Spectroscopy, Structure, and Reactivity of Stabilized Criegee IntermediatesAndrew J. Orr-Ewing*Andrew J. Orr-EwingSchool of Chemistry, University of Bristol, Bristol BS8 1TS, Unit…
View article: Unraveling the Ultrafast Photochemical Dynamics of Nitrobenzene in Aqueous Solution
Unraveling the Ultrafast Photochemical Dynamics of Nitrobenzene in Aqueous Solution Open
Nitroaromatic compounds are major constituents of the brown carbon aerosol particles in the troposphere that absorb near-ultraviolet (UV) and visible solar radiation and have a profound effect on the Earth's climate. The primary sources of…
View article: Trifluoroacetic Acid: Toxicity, Sources, Sinks and Future Prospects
Trifluoroacetic Acid: Toxicity, Sources, Sinks and Future Prospects Open
Trifluoroacetic acid (TFA) is a known and persistent pollutant in the environment. Although several direct anthropogenic sources exist, production from the atmospheric degradation of fluorocarbons such as some hydrofluorocarbons (HFCs) has…
View article: Exploring the ultrafast and isomer-dependent photodissociation of iodothiophenes <i>via</i> site-selective ionization
Exploring the ultrafast and isomer-dependent photodissociation of iodothiophenes <i>via</i> site-selective ionization Open
The dissociation dynamics of UV pumped iodothiophene molecules are investigated using velocity map ion imaging, in combination with site-selective extreme ultraviolet ionization of the iodine atom.
View article: Characterization of the Reversible Intersystem Crossing Dynamics of Organic Photocatalysts Using Transient Absorption Spectroscopy and Time-Resolved Fluorescence Spectroscopy
Characterization of the Reversible Intersystem Crossing Dynamics of Organic Photocatalysts Using Transient Absorption Spectroscopy and Time-Resolved Fluorescence Spectroscopy Open
Thermally activated delayed fluorescence (TADF) emitters are molecules of interest as homogeneous organic photocatalysts (OPCs) for photoredox chemistry. Here, three classes of OPC candidates are studied in dichloromethane (DCM) or N,N-dim…
View article: Early-Career and Emerging Researchers in Physical Chemistry Volume 2
Early-Career and Emerging Researchers in Physical Chemistry Volume 2 Open
ADVERTISEMENT RETURN TO ISSUESpecial Issue Prefac...Special Issue PrefaceNEXTEarly-Career and Emerging Researchers in Physical Chemistry Volume 2Anastassia N. AlexandrovaAnastassia N. AlexandrovaMore by Anastassia N. Alexandrovahttps://orc…
View article: Early-Career and Emerging Researchers in Physical Chemistry Volume 2
Early-Career and Emerging Researchers in Physical Chemistry Volume 2 Open
ADVERTISEMENT RETURN TO ISSUESpecial Issue Prefac...Special Issue PrefaceNEXTEarly-Career and Emerging Researchers in Physical Chemistry Volume 2Anastassia N. AlexandrovaAnastassia N. AlexandrovaMore by Anastassia N. Alexandrovahttps://orc…
View article: Direct momentum imaging of charge transfer following site-selective ionization
Direct momentum imaging of charge transfer following site-selective ionization Open
We study ultrafast charge rearrangement in dissociating 2-iodopropane (2-C3H7I) using site-selective core-ionization at the iodine atom. Clear signatures of electron transfer between the neutral propyl fragment and multiply charged iodine …
View article: Photoredox-HAT Catalysis for Primary Amine α-C–H Alkylation: Mechanistic Insight with Transient Absorption Spectroscopy
Photoredox-HAT Catalysis for Primary Amine α-C–H Alkylation: Mechanistic Insight with Transient Absorption Spectroscopy Open
The synergistic use of (organo)photoredox catalysts with hydrogen-atom transfer (HAT) cocatalysts has emerged as a powerful strategy for innate C(sp3)-H bond functionalization, particularly for C-H bonds α- to nitrogen. Azide ion (N3-) was…
View article: Evaluating the accuracy of absorbing aerosol optical properties measured using single particle cavity ring-down spectroscopy
Evaluating the accuracy of absorbing aerosol optical properties measured using single particle cavity ring-down spectroscopy Open
Single particle cavity ring-down spectroscopy (CRDS) allows direct and continuous measurements of the extinction cross-sections for levitated micron-scale aerosol particles of constant or evolving composition. Our recent interests have con…
View article: Charge-Separated Reactive Intermediates from the UV Photodissociation of Chlorobenzene in Solution
Charge-Separated Reactive Intermediates from the UV Photodissociation of Chlorobenzene in Solution Open
Although ultraviolet (UV)-induced photochemical cleavage of carbon-halogen bonds in gaseous halocarbons is mostly homolytic, the photolysis of chlorobenzene in solution has been proposed to produce a phenyl cation, c-C6H5+, which is a high…
View article: Ultrafast probing of charge transfer dynamics with an XUV free-electron laser
Ultrafast probing of charge transfer dynamics with an XUV free-electron laser Open
We study charge transfer in dissociating molecules of 2-iodopropane (C3H7I) in a UV pump – XUV probe regime at the SACLA free-electron laser. Signatures of charge transfer from the recently dissociated iodine atom to the neutral propyl rad…
View article: Direct Observation of the Dynamics of Ylide Solvation by Hydrogen-bond Donors Using Time-Resolved Infrared Spectroscopy
Direct Observation of the Dynamics of Ylide Solvation by Hydrogen-bond Donors Using Time-Resolved Infrared Spectroscopy Open
The photoexcitation of α-diazocarbonyl compounds produces singlet carbene intermediates that react with nucleophilic solvent molecules to form ylides. The zwitterionic nature of these newly formed ylides induces rapid changes in their inte…
View article: Accurate Measurement of the Optical Properties of Single Aerosol Particles Using Cavity Ring-Down Spectroscopy
Accurate Measurement of the Optical Properties of Single Aerosol Particles Using Cavity Ring-Down Spectroscopy Open
[Image: see text] New approaches for the sensitive and accurate quantification of aerosol optical properties are needed to improve the current understanding of the unique physical chemistry of airborne particles and to explore their roles …