A5069964985- Muon and positron interactions and applications
- Advanced NMR Techniques and Applications
- Ammonia Synthesis and Nitrogen Reduction
- Synthesis and characterization of novel inorganic/organometallic compounds
- NMR spectroscopy and applications
- Organoboron and organosilicon chemistry
- Atomic and Subatomic Physics Research
- Advancements in Battery Materials
- Hydrogen Storage and Materials
- Chemical Synthesis and Characterization
- Material Dynamics and Properties
- Synthesis and Properties of Aromatic Compounds
- Advanced Battery Materials and Technologies
- Advanced Condensed Matter Physics
- Advanced Chemical Physics Studies
- Electron Spin Resonance Studies
- Graphene research and applications
- Ionic liquids properties and applications
- Inorganic Fluorides and Related Compounds
- Topological Materials and Phenomena
- Particle Detector Development and Performance
- ZnO doping and properties
- Organometallic Complex Synthesis and Catalysis
- Liquid Crystal Research Advancements
- Atomic and Molecular Physics
Simon Fraser University
2015-2025
TRIUMF
2016-2025
University of Waterloo
2020-2025
Vancouver Biotech (Canada)
2017-2018
Rutherford Appleton Laboratory
2008-2015
Didcot Community Hospital
2015
Institute for Science and International Security
2010
Paul Scherrer Institute
2007-2009
University of Stuttgart
2005-2009
Muonium, and by analogy hydrogen, is shown to form a shallow-donor state in ${\text{In}}_{2}{\text{O}}_{3}$ ${\text{SnO}}_{2}$. The paramagnetic charge stable below $\ensuremath{\sim}50\text{ }\text{K}$ $\ensuremath{\sim}30\text{ ${\text{SnO}}_{2}$ which, coupled with its extremely small effective hyperfine splitting both cases, allows identification as the state. This has important implications for controversial issue of origins conductivity transparent conducting oxides.
The electrical nature of muonium in the transparent conducting oxide material Ga2O3 is investigated via muon-spin rotation and relaxation spectroscopy. It found to be a shallow donor, with an effective donor depth 15≤ED≤30 meV hyperfine splitting 0.13±0.01 MHz. This contrast deep level observed majority semiconductors but supports recent suggestion that should across class oxides. These observations suggest hydrogen will also Ga2O3, important implications both for unintentional conductivity...
The positive muon (μ+) can be incorporated into free radicals where it acts as a probe of the structure and dynamics. muoniated are characterized by series magnetic resonance techniques known μSR for spin rotation, relaxation spectroscopy. In this review is shown how used to obtain information about structure, dynamics, local environments transient in solids like zeolites, solution or even exotic solvents supercritical water. It will also demonstrated that probes complex systems, such...
Despite the great interest organic spintronics has recently attracted, there is only a partial understanding of fundamental physics behind electron spin relaxation in semiconductors. Mechanisms based on hyperfine interaction have been demonstrated, but role spin-orbit remains elusive. Here, we report muon spectroscopy and time-resolved photoluminescence measurements two series molecular semiconductors which strength systematically modified with targeted chemical substitution different atoms...
We have studied the interaction of three ortho-substituted benzoate anions (2-ethylbenzoate, 2-chlorobenzoate, and 2-hydroxybenzoate) para-substituted (4-ethylbenzoate, 4-chlorobenzoate, 4-hydroxybenzoate) with lamellar phase dispersions di-chain cationic surfactants 2,3-diheptadecyl ester ethoxypropyl-1,1,1-trimethyl-ammonium chloride (DHTAC) dioctadecyl-dimethyl-ammonium (DODMAC) using avoided level crossing muon spin resonance (ALC-μSR) spectroscopy. Highly polarized probes were produced...
One-electron oxidation of N-heterocyclic carbenes (NHCs) has been carried out using oxidising agents such as tetracyanoethylene (TCNE) and ferrocenium [Cp(2)Fe](+); the formation carbene radical cations is postulated.
Currently, no known material retains its photoinduced metallic conductivity over a long time while also exhibiting repeatable metal-to-insulator recovery. Here, we demonstrate such highly insulator-to-metal transition in yttrium oxyhydride (YOxHy) epitaxial thin films. The temperature (T) dependence of the electrical resistivity (ρ) films transforms from insulating to state (dρ/dT > 0) under ultraviolet laser illumination. YOxHy film recovers original when heated (125 °C) an Ar atmosphere...
The possible radicals resulting from hydrogen atom addition to the imidazole rings of 1,3-bis(isopropyl)-4,5-dimethylimidazol-2-ylidene (1) and 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene (2) have been studied by means density functional calculations (B3LYP). included solvent effects estimated via polarized continuum model (PCM) an empirical treatment vibrational averaging hyperfine constants. Addition a (or muonium) carbeneic carbon was found give radical 60.46 kJ mol(-)(1) more stable...
We report the NMR Knight shift and spin-lattice relaxation of $^{8}\mathrm{Li}{}^{+}$ implanted $\ensuremath{\sim}100$ nm into single crystals semimetallic Sb, Bi, topologically insulating ${\mathrm{Bi}}_{0.9}{\mathrm{Sb}}_{0.1}$. find small negative shifts (of order 100 ppm) in all three. In insulator, is nearly temperature independent, while Bi Sb it becomes more at low without following bulk susceptibility, suggesting two distinct dependent contributions, possibly from orbital spin...
Muonium has been used as an H atom analogue to investigate the free radicals formed by addition polyaromatic hydrocarbon fluoranthene. There are nine unique carbons in molecule, but only five were detected. Muon and proton hyperfine constants determined transverse field µSR µLCR, respectively, compared with calculated values. All signals assigned Mu C-H sites. is no evidence for tertiary at ring junctions.Key words: muonium, fluoranthene, radical, constants.
The high magnetic field (HiFi) muon instrument at the ISIS pulsed neutron and source is a state-of-the-art spectrometer designed to provide applied fields up 5 T for studies of condensed matter molecular systems. optimised time-differential spin relaxation source. We describe challenges involved in its design construction, detailing, particular, magnet detector performance. Commissioning experiments have been conducted results are presented demonstrate scientific capabilities new instrument.
β-Detected nuclear spin relaxation of (8)Li(+) has been used to study the microscopic diffusion lithium ions in thin films poly(ethylene oxide) (PEO), where implanted are present extremely low concentration, and PEO with 30 wt % LiCF3SO3 over a wide range temperatures both above below glass transition temperature. Recent measurements by Do et al. [Phys. Rev. Lett. 2013, 111, 018301] found that temperature dependence Li(+) conductivity was identical dielectric α well described...
We investigated the depth, temperature, and molecular-weight (MW) dependence of γ-relaxation in polystyrene glasses using implanted 8Li+ β-detected nuclear magnetic resonance. Measurements were performed on thin films with MW ranging from 1.1 to 641 kg/mol. The temperature average 8Li spin-lattice relaxation time (T1avg) was measured near free surface bulk. Spin-lattice is caused by phenyl ring flips, which involve transitions between local minima over free-energy barriers enthalpic entropic...
Computational docking reveals the influence of conformation on inhibition cytochrome P450 3A4. Such structure–activity relationships are dependent intra-molecular interactions in cannabinoids, forming stabilised coiled structures.
Avoided level crossing muon spin resonance (ALC-μSR) is used to characterize muoniated free radicals. These radicals are as probes of the local environment and reorientational motion specific components in complex systems. The parameter that provides information about anisotropic motionally-averaged dipolar-hyperfine coupling constant (Dμ‖). ALC-μSR spectra environments frequently have Lorentzian-like Δ1 resonances, which makes it challenging extract Dμ‖. In this paper, we derive a means...
β-detected nuclear spin relaxation of 8Li+ has been used to probe the depth dependence molecular dynamics in high- and low-molecular-weight deuterated polystyrene. The average spin–lattice rate, 1/Tavg1, is a measure spectral density polymer motion at Larmor frequency (41 MHz 6.55 T). In both samples, 1/Tavg1 independent below ∼200 K but above this temperature it decreases approximately exponentially with distance from free surface, returning bulk behavior for depths greater than ∼10 nm....
β-NMR measurements indicate there is enhanced phenyl ring dynamics near the free surface in polystyrene thin films.
New evidence is presented for the observation of a muoniated radical in Mu + Br(2) system, from μSR longitudinal field (LF) repolarisation studies gas phase, at concentrations 0.1 bar Br(2)/N(2) mixture 300 K and 10 total pressure. The LF curve, up to 4.5 kG, reveals two paramagnetic components, one atom, formed promptly during slowing-down process positive muon, with known hyperfine coupling constant (hfcc) 4463 MHz, by fast addition. From model fits data, component found have an unusually...
Electron spin relaxation rate (eSR) is investigated on several organic semiconductors of different morphologies and molecular structures, using avoided level crossing muon spectroscopy as a local probe. We find that two functionalized acenes (polycrystalline tri(isopropyl)silyl-pentacene amorphous 5,6,11,12-tetraphenyltetracene) exhibit eSRs with an Arrhenius-like temperature dependence, each characteristic energy scales similar to those expected from vibrations. Polycrystalline...
A 1,3-diphosphacyclobutane-2,4-diyl contains a unique unsaturated cyclic unit, and the presence of radical-type centers have been expected as source functionality. This study demonstrates that P-heterocyclic singlet biradical captures muonium (Mu=[μ+ e- ]), light isotope hydrogen radical, to generate an observable paramagnetic species. Investigation powder sample 2,4-bis(2,4,6-tri-t-butylphenyl)-1-t-butyl-3-benzyl-1,3-diphosphacyclobutane-2,4-diyl using muon (avoided) level-crossing...
Abstract Muonium (Mu), an H atom analogue, is employed to probe the addition of free radicals P=C bond a phosphaalkene. Specifically, two unprecedented muoniated radicals, MesP . −CMu(Me) 2 ( 1 , minor product) and MesPMu−C Me b major product), were detected by muon spin spectroscopy (μSR) when solution MesP=CMe : Mes=2,4,6‐trimethylphenyl) was exposed beam positive muons (μ + ). The μ serves as source Mu (that is, Mu=μ +e − To confirm identity product its spectral features compared...