A5006447521- Advanced Chemical Physics Studies
- Photochemistry and Electron Transfer Studies
- Spectroscopy and Quantum Chemical Studies
- Mass Spectrometry Techniques and Applications
- Laser-Matter Interactions and Applications
- Water-Energy-Food Nexus Studies
- DNA and Nucleic Acid Chemistry
- X-ray Spectroscopy and Fluorescence Analysis
- Atomic and Subatomic Physics Research
- Water resources management and optimization
- Molecular spectroscopy and chirality
- Spectroscopy and Laser Applications
- Ion-surface interactions and analysis
- Advanced X-ray Imaging Techniques
- melanin and skin pigmentation
- Biochemical Analysis and Sensing Techniques
- Free Radicals and Antioxidants
- Atomic and Molecular Physics
- Radioactive element chemistry and processing
- Chemical Reactions and Mechanisms
- Hydrology and Watershed Management Studies
- Diamond and Carbon-based Materials Research
- Photovoltaic System Optimization Techniques
- Transboundary Water Resource Management
- Molecular Spectroscopy and Structure
Heriot-Watt University
2015-2025
Brown University
2024
United Nations Environment Programme
2022-2023
University of Bristol
2020-2023
University of Oxford
2020
Oxford Research Group
2020
Northrop Grumman (United States)
2016
Integrated water resources management (IWRM) has been central to governance and worldwide since the 1990s. Recognizing significance of an integrated approach as a way achieve Sustainable Development Goals (SDGs), IWRM was formally incorporated part SDG global indicator framework, thus committing UN its Member States achieving high implementation by 2030 measuring progress through 6.5.1. This paper examines extent which improves sustainable health water-related ecosystems-a first-of-its-kind...
Abstract Various photoactive molecules contain motifs built on aza-aromatic heterocycles, although a detailed understanding of the excited state photophysics and photochemistry in such systems is not fully developed. To help address this issue, non-adiabatic dynamics operating azanaphthalenes under hexane solvation was studied following 267 nm excitation using ultrafast transient absorption spectroscopy. Specifically, species quinoline, isoquinoline, quinazoline, quinoxaline,...
Time-resolved photoelectron imaging was used to investigate the electronic relaxation dynamics of gas-phase aniline, N, N-dimethylaniline, and 3,5-dimethylaniline following ultraviolet excitation at 250 nm. Our analysis supported by ab initio coupled-cluster calculations evaluating excited state energies (in aniline) evolution a range physical properties as function N–H bond extension. Due lack consistency between several earlier studies undertaken in specific aim this present work gain new...
Abstract The detailed features of molecular photochemistry are key to understanding chemical processes enabled by non-adiabatic transitions between potential energy surfaces. But even in a small molecule like hydrogen sulphide (H 2 S), the influence is not yet well understood. Here we report high resolution translational spectroscopy measurements H and S( 1 D) photoproducts formed following excitation S selected quantum levels Rydberg state with B electronic symmetry at wavelengths λ ~ 139.1...
We present an initial demonstration of a velocity-map imaging (VMI) experiment using back-irradiation laser-based desorption source directly integrated into the electrode assembly. This has potential to greatly expand utility popular VMI approach by permitting its use with high density plumes non-volatile molecular samples. Photoelectron circular dichroism measurements on phenylalanine molecule 400 nm multiphoton ionization are used illustrate this novel method, revealing forward-backward...
Time-resolved photoelectron spectroscopy reveals distinct ionization signatures of Rydberg-to-valence state evolution in the secondary aliphatic amine piperidine.
Wavelength-dependent measurements of the RNA base uracil, undertaken with nanosecond ultraviolet laser pulses, have previously identified a fragment at m/z = 84 (corresponding to C3H4N2O+ ion) excitation wavelengths ≤232 nm. This has been interpreted as possible signature theoretically predicted ultrafast ring-opening occurring on neutral excited state potential energy surface. To further investigate dynamics this mechanism, and also non-adiabatic operating more generally in we used newly...
The comprehensive picture of the fragmentation behaviour H 2 S has been provided by detecting H, S( 1 D) and S) atom products at wavelengths 155–120 nm.
Excess energy redistribution dynamics operating in nitrobenzene under hexane and isopropanol solvation were investigated using ultrafast transient absorption spectroscopy (TAS) with a 267 nm pump 340-750 white light continuum probe. The use of nonpolar solvent provides proxy to the gas-phase environment, findings are directly compared recent time-resolved photoelectron imaging (TRPEI) study on same excitation wavelength [L. Saalbach et al., J. Phys. Chem. A 2021, 125, 7174-7184]. Of note is...
Coulomb explosion velocity-map imaging is a new and potentially universal probe for gas-phase chemical dynamics studies, capable of yielding direct information on (time-evolving) molecular structure. The approach relies detailed understanding the mapping between initial atomic positions within structure interest final velocities fragments formed via explosion. Comprehensive on-the-fly ab initio trajectory studies are presented two prototypical small molecules, formyl chloride...
C-I bond extension and fission following ultraviolet (UV, 262 nm) photoexcitation of 2- 3-iodothiophene is studied using ultrafast time-resolved extreme (XUV) ionization in conjunction with velocity map ion imaging. The photoexcited molecules eventual I atom products are probed by site-selective at the 4d edge intense XUV pulses, which induce multiple charges initially localized to iodine atom. At separations below critical distance for charge transfer (CT), can redistribute around molecule...
We present results from a recent time-resolved photoelectron imaging (TRPEI) study investigating the non-adiabatic relaxation dynamics of <italic>N</italic>,<italic>N</italic>-dimethylaniline (<italic>N</italic>,<italic>N</italic>-DMA) and 3,5-dimethylaniline (3,5-DMA) following excitation at 240 nm. Analysis experimental data is supported by <italic>ab initio</italic> coupled-cluster calculations evaluating excited state energies evolution several physical properties as function...
Time-resolved photoelectron imaging was used to investigate nonadiabatic processes operating in the excited electronic states of nitrobenzene and three methyl-substituted derivatives: 3,5-, 2,6-, 2,4-dimethylnitrobenzene. The primary goal evaluating dynamical impact torsional angle between NO2 group benzene ring plane—something previously implicated mediating propensity for branching into different photodissociation pathways (NO vs elimination). Targeted, photoinitiated release NO radicals...
The advanced electrical power system (AEPS) is the first remote, resilient dc microgrid for mission-critical space applications. This structured features resiliency, energy balancing, autonomy, standard interface, fault tolerance, isolation, modularity, and scalability. basic building modules are described. Typical configurations then presented to illustrate its versatility ability reduce cost. Fault-tolerant design principles discussed. A-minute-day simulation demonstrate system-level...
Femtosecond pulses of light in the vacuum ultraviolet (VUV) spectral region permit extended observation non-adiabatic dynamics gas-phase molecules. When used as a probe time-resolved photoelectron spectroscopy, such project deeply into ionization continuum and allow evolution excited state population to be monitored across multiple potential energy surfaces. compared with longer-wavelength probes, this often provides more complete view along reaction coordinate(s) connecting photoreactants...
We report time-resolved photoelectron imaging studies of gas-phase pyrrole over the 267-240 nm excitation region, recorded in conjunction with a 300 probe. Of specific interest is lowest-lying (3s/πσ*) state, which exhibits very weak oscillator strength but thought to be excited directly at wavelengths ≤254 nm. conclude, however, that only significant contribution our data all investigated from non-resonant ionization. Our findings do not rule out state (as appears confirmed by supporting...
Laser-based thermal desorption facilitates the first gas-phase study of ultrafast non-adiabatic dynamics operating in 5,6-dihydroxyinole following ultraviolet excitation.
The Coulomb explosion (CE) of jet-cooled CH3I molecules using ultrashort (40 fs), nonresonant 805 nm strong-field ionization at three peak intensities (260, 650, and 1300 TW cm-2) has been investigated by multimass velocity map imaging, revealing an array discernible fragment ions, that is, Iq+ (q ≤ 6), CHn+ (n = 0-3), CHn2+ 0, 2), C3+, H+, H2+, H3+. Complementary ab initio trajectory calculations the CE CH3IZ+ cations with Z 14 identify a range behaviors. parent 2 3 can be well-described...
The dynamics of cyclopentadiene (CP) following optical excitation at 243 nm was investigated by time-resolved pump–probe X-ray scattering using 16.2 keV X-rays the Linac Coherent Light Source (LCLS). We present first ultrafast structural evidence that reaction leads directly to formation bicyclo[2.1.0]pentene (BP), a strained molecule with three- and four-membered rings. bicyclic compound decays via thermal backreaction vibrationally hot CP time constant 21 ± 3 ps. A minor channel...
Abstract Advances in x-ray free electron lasers have made ultrafast scattering a powerful method for investigating molecular reaction kinetics and dynamics. Accurate measurement of the ground-state, static signals reacting molecules is pivotal these pump-probe experiments as they are cornerstone interpreting observed structural This article presents data calibration procedure, designed gas-phase conducted at Linac Coherent Light Source Free-Electron Laser SLAC National Accelerator...
Integrated water resources management (IWRM) has been central to governance and worldwide since the 1990s. Recognizing significance of an integrated approach as a way achieve Sustainable Development Goals (SDGs), IWRM was formally incorporated part SDG global indicator framework, thus committing UN its Member States achieving high implementation measuring progress through 6.5.1. This paper examines extent which improves sustainable health water-related ecosystems—a first-of-its-kind in terms...