A5035561177- Advanced NMR Techniques and Applications
- Solid-state spectroscopy and crystallography
- Molecular spectroscopy and chirality
- Quantum, superfluid, helium dynamics
- Advanced Chemical Physics Studies
- Molecular Spectroscopy and Structure
- Spectroscopy and Quantum Chemical Studies
- Atomic and Subatomic Physics Research
- Fullerene Chemistry and Applications
- Crystallography and molecular interactions
- Electron Spin Resonance Studies
- NMR spectroscopy and applications
- Astrophysics and Star Formation Studies
- Advanced MRI Techniques and Applications
- High-pressure geophysics and materials
- X-ray Diffraction in Crystallography
- Quantum optics and atomic interactions
- Crystallization and Solubility Studies
- Nonlinear Dynamics and Pattern Formation
- Mechanical and Optical Resonators
- Organic and Molecular Conductors Research
- Atomic and Molecular Physics
- Crystal structures of chemical compounds
- Magnetism in coordination complexes
- Quantum chaos and dynamical systems
University of Nottingham
2011-2022
Centre National de la Recherche Scientifique
1997
Université Joseph Fourier
1997
KU Leuven
1983-1994
University of Surrey
1989
University of Sheffield
1979-1981
Inelastic neutron scattering, far-infrared spectroscopy, and cryogenic nuclear magnetic resonance are used to investigate the quantized rotation ortho–para conversion of single water molecules trapped inside closed fullerene cages. The existence metastable ortho -water is demonstrated, interconversion -and para spin isomers tracked in real time. Our investigation reveals that ground state encapsulated has a lifted degeneracy, associated with symmetry-breaking environment.
Evidence is presented which suggests that the thermally activated reorientation rate tau -1 of methyl groups in a very wide range solids closely follows universal law relates to hindering barrier height V and temperature theta . Thus simply measures with calibration curve dependent on V. A simple theory curves described, using thermal average over all group torsion-rotation states modulus expectation value angular momentum. No adjustable parameters are involved if cosine potential assumed....
Using low temperature dynamic nuclear polarisation (DNP) in conjunction with dissolution makes it possible to generate highly polarised spin systems for liquid state applications of magnetic resonance spectroscopy. However, its current implementation, which requires the transfer solute between two different magnets, hyperpolarisation strategy is limited relatively long longitudinal relaxation time constants. Here we describe design and construction a dedicated spectrometer DNP that based on...
The water-endofullerene H2O@C60 provides a unique chemical system in which freely rotating water molecules are confined inside homogeneous and symmetrical carbon cages. spin conversion between the ortho para species of endohedral H2O was studied solid phase by low-temperature nuclear magnetic resonance. experimental data consistent with second-order kinetics, indicating bimolecular process. Numerical simulations suggest simultaneous presence diffusion process allowing neighbouring to...
The splitting of the <italic>ortho</italic>-H<sub>2</sub>O ground state is clearly revealed by inelastic neutron scattering.
We present an overview of solid-state NMR studies endohedral H2-fullerene complexes, including 1H and 13C spectra, spin relaxation studies, the results dipole–dipole recoupling experiments. The available data involves three different studied over a wide range temperatures applied magnetic fields. symmetry cage influences strongly motionally-averaged nuclear interactions H2 species, as well its behaviour. In addition, non-bonding between fullerene cages are influenced by presence hydrogen...
The proton hyperfine coupling tensors in the Cu(H2O)6 2+ ion Mg(NH4)2(SO4)2.6H2O single crystals at 15 K have been measured by ENDOR spectroscopy. values obtained are discussed framework of conventional molecular orbital theory for copper complexes and can be understood quite satisfactorily. geometry appears similar to that pure Cu(NH4)2(SO4)2.6H2O.
In low-field nuclear magnetic resonance in solids, transitions are not driven directly by the oscillating field, but dipole-dipole interactions modulated applied field. This results strong \ensuremath{\Delta}m=2 due to internal field gradients. Tunnel sidebands, symmetry forbidden ordinary NMR, become strongly allowed. frequencies of rotating molecular groups measured a previously inaccessible frequency range.
We report an inelastic neutron scattering investigation of the quantum dynamics hydrogen molecules trapped inside anisotropic fullerene cages. Transitions among manifold quantized rotational and translational states are directly observed. The spectra recorded as a function energy momentum transfer interpreted in terms potential cage dimensions. thermodynamics orthohydrogen parahydrogen investigated through temperature dependence measurements.
A strong correlation is demonstrated between two parameters connected with methyl group motion, and measured in a wide variety of solids. The are h nu t, the tunnel splitting ground torsional state, theta min, temperature at which rate constant tau -1 associated thermally activated reorientation has value 2*108s-1. results suggest that there exists universal law form f( , -1, )=0 governing ( ) dependence -1. This independent phonon spectrum host lattice, conflict much recent theoretical work...
We report an inelastic neutron-scattering (INS) investigation of coupled quantum translation and rotation hydrogen molecules trapped inside the closed isotropic cages ${\text{C}}_{60}$. The low-lying states that characterize translation-rotation manifold are accurately determined in our study INS peak energies. A comparison between spectra ${\text{H}}_{2}$ HD isotopomers provides quantitative insight into coupling rotational translational angular momentum with exhibiting strongest effects...
The quantum dynamics of dihydrogen molecules entrapped inside fullerene cages has been investigated using inelastic neutron scattering (INS). For the endofullerene H${}_{2}$@C${}_{60}$ low-lying energy levels manifold coupled translational and rotational states have accurately determined by studying INS spectra recorded in temperature range $1.5\ensuremath{\leqslant}T\ensuremath{\leqslant}240\phantom{\rule{0.16em}{0ex}}\mathrm{K}$. majority transitions observed interconvert nuclear spin...
Vibrational spectra of several isotopomers benzoic acid (BA) crystals have been recorded by inelastic neutron scattering and are compared with calculated for different potential energy surfaces (PES). These PES were obtained within the harmonic approximation from quantum chemical density functional theory (DFT) calculations made monomer, isolated dimer, crystal using codes levels basis functions. Without refinement force constants, agreement between observed is already sufficient an...
The dynamics of proton transfer along the hydrogen bonds dimers benzoic acid has been characterized in single crystals and powders at temperatures between 10 K 110 by quasi-elastic neutron scattering (QENS) spin-lattice relaxation using field-cycling NMR spectroscopy. These measurements define geometry transfer, energy difference two tautomers corresponding to positions, as well correlation time. jump vector agrees with expectations from recent crystallographic data. A/kB=86.5±1.5 is...
The techniques of pulsed NMR spectroscopy and inelastic neutron scattering (INS) have been employed to study the coordinated motion hydrogen atoms in bonds carboxylic acid dimers. proton spin-lattice relaxation time T1 has measured at two frequencies diglycolic suberic reorientation rate directly by quasi-elastic scattering. Furthermore data collected on benzoic acid, terephthalic malonic different spectrometer those earlier published data. INS successfully fitted a new model proposed...
The dynamics of hydrogen atoms in the bonds benzoic acid dimers have been studied as a function hydrostatic pressure to pressures excess 4 kbar. This paper is primarily concerned with results up 3.3 temperature dependence correlation time for motion at series has investigated using measurements proton spin–lattice relaxation time. Strong non-Arrhenius behavior exhibited and data are good agreement model which invokes phonon assisted tunneling low thermally activated Arrhenius high...
The isotope effects associated with double proton transfer in the hydrogen bonds of benzoic acid (BA) dimers have been measured using field-cycling (1)H NMR relaxometry and quasielastic neutron scattering. By studying mixed (hydrogen deuterium) samples, dynamics three isotopologues, BA-HH, BA-HD, BA-DD, investigated. Low temperature measurements provide accurate incoherent tunneling rate, k(0). This parameter scales accurately mass number, m, according to formula k(0)=(E/m)e(-Fm) providing...
We have observed 1H NMR spectra of hydrogen molecules trapped inside modified fullerene cages under cryogenic conditions. Experiments on static samples were performed at sample temperatures down to 4.3 K, while magic-angle-spinning (MAS) experiments 20 K spinning frequencies 15 kHz. Both types show a large increase in the intramolecular 1H-1H dipolar coupling below 50 revealing thermal selection small number spatial rotational states. The and MAS compared estimate degree heating high-speed...
Solid toluene has been studied in its α phase at 5K by high resolution Inelastic Neutron Scattering (I.N.S.). The tunnel splitting of the methyl torsion group state found to be 0.196 cm −1 (24.3 μeV) for C 6 D 5 CH 3 and 0.0088 (1.1 CD . Simple cosine (V , V ) or square well potentials are able reproduce this but calculated first torsional transitions (∼56 then slightly higher than value 46.8 deduced from analysis Raman I.N.S. spectra obtained several isotopic derivatives a large temperature...
The quantum dynamics of a hydrogen molecule encapsulated inside the cage C60 fullerene is investigated using inelastic neutron scattering (INS). emphasis on temperature dependence INS spectra which were recorded time-of-flight spectrometers. endofullerene system highly mechanical, exhibiting both translational and rotational quantization. profound influence Pauli exclusion principle revealed through nuclear spin isomerism. shown to be exceptionally able drive transitions between...