A5040141914- Spectroscopy and Quantum Chemical Studies
- Theoretical and Computational Physics
- Advanced Chemical Physics Studies
- Physics of Superconductivity and Magnetism
- Planetary Science and Exploration
- Crystallography and molecular interactions
- Quantum many-body systems
- Free Radicals and Antioxidants
- Astro and Planetary Science
- Photochemistry and Electron Transfer Studies
- Protein Structure and Dynamics
- Mass Spectrometry Techniques and Applications
- Advanced NMR Techniques and Applications
- Molecular spectroscopy and chirality
- Molecular Spectroscopy and Structure
- Methane Hydrates and Related Phenomena
- Solid-state spectroscopy and crystallography
- Advanced Condensed Matter Physics
- Chemical Thermodynamics and Molecular Structure
- Spectroscopy and Laser Applications
- Atomic and Subatomic Physics Research
- Material Dynamics and Properties
- Electron Spin Resonance Studies
- Nitric Oxide and Endothelin Effects
- Atmospheric chemistry and aerosols
Aarhus University
2012-2023
California Institute of Technology
2002-2008
University of Regina
2004
University of Toronto
2001-2003
McMaster University
2003
University of Szeged
2003
NTT Basic Research Laboratories
2002
University of North Texas
2001
Institute of Organic Chemistry
2001
Semmelweis University
2001
The internal energy and the order parameter of three-state Potts model in a simple cubic lattice are calculated using Monte Carlo technique. Both properties exhibit metastabilities small temperature region demonstrating that phase transition is first order. This result agreement with prediction $\ensuremath{\epsilon}$ expansion but contrast to position-space renormalization-group calculations which lead continuous transition.
Aqueous nitrate, NO3(-)(aq), was studied by 2D-IR, UV-IR, and UV-UV time-resolved spectroscopies in combination with molecular dynamics (MD) simulations the purpose of determining hydration around anion. In water, D3h symmetry NO3(-) is broken, degeneracy asymmetric-stretch modes lifted. This provides a very sensitive probe ion-water interactions. The 2D-IR measurements reveal excitation exchange between two nondegenerate vibrations on 300-fs time scale concomitant fast anisotropy decay...
We present data on the inclusive scattering of polarized electrons from a 3He target at energies 0.862 to 5.06 GeV, obtained angle 15.5°. Our include measurements quasielastic peak, through nucleon resonance region, and beyond, were used determine virtual photon cross-section difference σ1/2−σ3/2. extract extended Gerasimov-Drell-Hearn integral for neutron in range four-momentum transfer squared Q2 0.1–0.9 GeV2.Received 15 May 2002DOI:https://doi.org/10.1103/PhysRevLett.89.242301©2002...
We have measured the spin structure functions $g_1$ and $g_2$ of $^3$He in a double-spin experiment by inclusively scattering polarized electrons at energies ranging from 0.862 to 5.07 GeV off target 15.5$^{\circ}$ angle. Excitation covered resonance onset deep inelastic regions. determined for first time $Q^2$ evolution $\Gamma_1(Q^2)=\int_0^{1} g_1(x,Q^2) dx$, $\Gamma_2(Q^2)=\int_0^1 g_2(x,Q^2) dx$ $d_2 (Q^2) = \int_0^1 x^2[ 2g_1(x,Q^2) + 3g_2(x,Q^2)] neutron range 0.1 GeV$^2$ $\leq Q^2...
ESR spectra of KClO4 crystals irradiated with x rays at 10 and 26°K contain three “families” intense signals. The signals are assumed to derive from primary defects constituted by electrons holes trapped on ClO4− ions. families assigned the species ClO4=, ClO4, (ClO4)2−, each in a number distinct sites. ClO4= ClO4 appear be stabilized intraionic configuration change, whereas interionic change may stabilize (ClO4)2−. Thermal processes starting 30°K result formation secondary O3− ClO2 destruction
Accurate spin Hamiltonians for one paramagnetic center in irradiated KClO4 are derived from ESR spectra at five temperatures the range −170° to 0°C. The quadrupole interaction gives rise ``forbidden'' transitions of high intensity. An iterative procedure is used computation principal values g tensor as well tensors magnetic and electric hyperfine interaction. Comparison low-temperature Hamiltonian with that microwave free ClO2 molecule demonstrates adequately described terms a trapped...
Analytical expressions for the sixth and eighth moments of magnetic-resonance lines a dipolar-coupled rigid lattice are obtained by performing commutations angular momentum operators necessary reductions means computer. The used to derive numerical values simple cubic varying numbers interacting neighbors. predicted from Abragam's trial function free-induction-decay curve compared corresponding exact reported here. We also present straightforward method algebraic computer calculation traces...
The generalized forward spin polarizabilities γ0 and δLT of the neutron have been extracted for first time in a Q2 range from 0.1 to 0.9 GeV2. Since is sensitive nucleon resonances insensitive Δ resonance, it expected that pair should provide benchmark tests current understanding chiral dynamics QCD. new results on show significant disagreement with perturbation theory calculations, while data at low are good agreement next-to-leading-order relativistic baryon calculation. phenomenological...
The critical behavior of a three-dimensional antiferromagnet described by six-dimensional order parameter has been investigated the Monte Carlo technique. A first-order phase transition is observed. This result in agreement with prediction renormalization-group calculations $4\ensuremath{-}\ensuremath{\epsilon}$ dimensions and neutron scattering experiments on U${\mathrm{O}}_{2}$, but contrast to mean-field theory, which leads second-order transition.
This paper reports an experimental study of the photolysis aqueous HOCl using femtosecond pulses at 266 nm. The formation photoproducts is monitored by transient absorption spectroscopy from 230 to 400 molecules dissociate with unity quantum yield form OH+Cl faster than 1 ps, and as a result potential along HO–Cl reaction coordinate, all excess energy given fragments translational energy. After dissociation, solvent cage escape, majority Cl OH recombine after diffusion on time scale 50 ps....
The Ising model considered by von Boehm and Bak [Phys. Rev. Lett. 42, 122 (1979)] is studied in a spin-\textonehalf{} version with the spins arrayed on simple cubic lattice. uniaxial ferromagnetic interaction between nearest-neighbor $\mathrm{xy}$ planes competing interactions next-nearest-neighbor $z$ direction. phase transitions of are mean-field Monte Carlo calculations for same set parameters as chosen Bak. suggest that wave vector $q$, function temperature, picks up every rational...
Hydrogen bonds involving the methyl group have been studied by topological analysis of electron density derived from quantum mechanical geometry-optimized structures selected molecules/ions. The results indicate that hydrogen-bond formation not only depends on distance to proton acceptor, X, but also angle CH···X. species investigated suggest should be bigger than about 100° for formation.
Certain physical systems are expected classically to exhibit second-order phase transitions but known have first-order within the renormalization-group approach because no stable fixed point exists. This lack of points is caused by fluctuations in order parameter and depends only upon symmetry system. When a symmetry-breaking field applied may emerge continuous transition becomes possible. We studied this crossover from three different approaches. Our model has cubic magnetic ground state...
The order parameter $\ensuremath{\Phi}$ of the four-dimensional simple hypercubic spin-\textonehalf{} Ising ferromagnet is calculated by Monte Carlo technique. data, which may be represented $\ensuremath{\Phi}(t)=B{(\ensuremath{-}t)}^{\frac{1}{2}}{|\mathrm{ln}(\ensuremath{-}t)|}^{\frac{1}{3}}$ with $1.53<B<1.56$ for $0.005<\ensuremath{-}t\ensuremath{\equiv}\frac{({T}_{c}\ensuremath{-}T)}{{T}_{c}}<0.40$, supports theoretical prediction a multiplicative logarithmic correction to...
A molecular-dynamics experiment is used to derive free-induction-decay curves for a rigid cubic lattice with 216 classical spins coupled by magnetic dipole interaction. Free-induction-decay are obtained the field along [100], [110], and [111] axes of lattice. The shapes these compared derived from expansion theory Gade Lowe based on Abragam's trial function. considerable difference found between predictions our experiments, whereas functions reproduce experiments quite well except long...
A molecular theory of diffusion constants in liquids, independent model, is developed the language time-dependent correlation functions and statistical projection operators. Diffusion are related to friction which turn depend upon force autocorrelation with a time dependence arising from Liouville operator projected orthogonally momentum. The resulting expressions those previously obtained ``projected'' connected dissipation momentum, i.e., considered by Kirkwood. influence translations on...
The Monte Carlo technique is applied to a study of the phase transitions and critical behavior spin-\textonehalf{} Ising model on an fcc lattice with mixtures two- (${J}_{2}$) four - (${J}_{4}$) spin interactions. In limit ${J}_{2}=0$ exhibits first-order transition. transition remains first order for $\frac{{J}_{4}}{{J}_{2}}\ensuremath{\gtrsim}\frac{1}{2}$, but crossover continuous found around $\frac{{J}_{4}}{{J}_{2}}\ensuremath{\approx}\frac{1}{4}\ensuremath{-}\frac{1}{2}$ indicating that...
We present a measurement of the spin-dependent cross sections for 3He over -->(e -->,e')X reaction in quasielastic and resonance regions at four-momentum transfer 0.1< or =Q2< =0.9 GeV2. The spin-structure functions have been extracted used to evaluate nuclear Burkhardt-Cottingham extended Gerasimov-Drell-Hearn sum rules first time. data are also compared an impulse approximation calculation exact three-body Faddeev region.
The Monte Carlo technique is used to calculate the static properties of spin systems with an interaction described by a secular dipolar Hamiltonian finite range interaction. spins are arranged in simple cubic lattice periodic boundary conditions. structures determined for magnetic field along three directions [001], [110], and [111], both at positive negative temperatures. structures, which antiferromagnetic type, compared predictions based on mean-field theory NMR experiments...