Papers by Kenneth Jeffrey
Solid State Ionics, May 1, 1997
Aqueous and organic solutions of strong acids such as H3PO4 have been entrapped in various polyme... more Aqueous and organic solutions of strong acids such as H3PO4 have been entrapped in various polymeric gels synthesized within the acid solutions. Electrolytes based on poly(acrylamide) hydrogels with H3PO4 additives were cast as films and exhibited room temperature protonic conductivities greater than 10−2 Scm−1. Both acid and water concentrations influence the proton transport mechanisms. Nonaqueous protonic gels incorporating H3PO4 have
Zeitschrift für Naturforschung, 1995
The molecular dynamics of solid (CH3)3NBH3 is investigated by deuterium NMR spectroscopy. Variabl... more The molecular dynamics of solid (CH3)3NBH3 is investigated by deuterium NMR spectroscopy. Variable temperature lineshape analyses yield activation energies of 27 + 3, 19 + 2, and 12.5 ± 2 kJ/mol for-CH3,-N(CH3)3 and-BH3 rotation, respectively. Analysis of the temperature depen dence of the spin-lattice relaxation times, Tt , gives activation energies of 33 + 3, 15 + 1.5, and 14 + 1.5 kJ/mol, respectively. Direct comparison of rotational exchange rates (from lineshape simu lations) an of rotational correlation times (from Tx analyses) for-N(CH3)3 and-BH3 rotation indicate that the two motions are correlated in solid (CH3)3NBH3 and together constitute a whole molecule reorientation about the N-B bond. This is supported by an internal rotational barrier of 18.0 kJ/mol for-BH3 rotation, obtained from ab initio molecular orbital calculations at the MP2/6-31G* level.
This article discusses the application of NMR spectroscopy to the study of structural phase trans... more This article discusses the application of NMR spectroscopy to the study of structural phase transitions in solids. The various classifications of solid-solid phase transitions are presented. The changes in NMR lineshapes that accompany site symmetry changes during a phase transition are explained. The order-disorder and displacive phase transitions are described as well as how these two types of phase transitions can be distinguished by NMR spectroscopy. Changes in molecular and atomic dynamics frequently occur during structural phase changes. A description of how these changes affect NMR lineshapes and relaxation times is presented. A brief explanation of how Landau theory can be used to relate NMR spectroscopy and structural phase transitions is also presented. Keywords: phase transitions; NMR spectroscopy; Landau theory; displacive phase transition; order-disorder phase transition; soft modes; spin-lattice relaxation; quadrupolar coupling constant; chemical shift
Springer eBooks, Jul 7, 2008
ABSTRACT The long-established method of distinguishing between heterogeneous and homogeneous line... more ABSTRACT The long-established method of distinguishing between heterogeneous and homogeneous line shapes was introduced in the seminal paper by Bloembergen et al. [1]. The differentiation between the two types of spectral lines is based on whether one can alter the shape or just the amplitude of a line by an external perturbation. This concept has been applied many times particularly in optical hole burning spectroscopy where the distribution of transition frequencies can often be traced back to structural inhomogeneities in the material under study. It is well known that the frequency of an electronic transition, for example, sensitively depends on the local symmetry. This technique has been successfully applied to the structural elucidation of glasses [2].
Thermochimica Acta, Nov 1, 1985
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Solid State Nuclear Magnetic Resonance, Nov 1, 2008
In anticipation of using fluctuations in the nuclear dipolar and quadrupolar interaction as a pro... more In anticipation of using fluctuations in the nuclear dipolar and quadrupolar interaction as a probe of lithium ion motion in lithium borate glasses, the static values of these interactions were measured using a variety of echo techniques. The static quadrupolar echo spectrum of 7 Li and a calculation of the dipolar interaction in crystalline Li 2 B 4 O 7 (same chemical composition as the glass under study) were used to estimate the strength of the two interactions. These indicate that the dipolar and quadrupolar interactions for 6 Li will be of similar size and the dipolar interaction will be dominated by the unlike spin interaction between the 6 Li and the 10 B, 11 B spins. An appropriate theoretical model is proposed and explicit expressions for the echo amplitude are calculated in terms of the dipolar and quadrupolar second moments. This single spin model takes into account the quadrupolar interaction but treats the dipolar interaction as an effective magnetic field. Experimental results are presented which show the essential validity of the model and measurements lead to reasonable values for the dipolar and quadrupolar second moments. The relative merits of the various echo techniques are discussed.
Journal of Physics C: Solid State Physics, Feb 14, 1973
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Journal of magnetic resonance, Jul 1, 1976
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Canadian Journal of Chemistry, Dec 1, 1995
Deuterium nuclear magnetic resonance (NMR) spectra and spin-lattice relaxation times (TI) are use... more Deuterium nuclear magnetic resonance (NMR) spectra and spin-lattice relaxation times (TI) are used to investigate the dynamics of the guest molecule, acetone, in tris(5-acetyl-3-thieny1)methane (TATM) and cyclotriveratrylene (CTV) inclusion compounds. I3C CPMAS powder NMR spectra were obtained for each clathrate, to verify inclusion. In acetone: TATM, the guest molecule is undergoing twofold reorientation about the CO bond, exchanging the two methyl groups. An activation energy of 20.8 (*1.4) kJImol, for the two-site jump motion, was found, independently, from deuterium NMR spectra and TI measurements. Acetone in CTV performs the same type of motion as acetone in TATM. Activation energies of 25.0 (f3.2) kJ/mol and 24.1 (f0.5) Wlmol were determined using the same two techniques. In both inclusion compounds, the rate of methyl rotation within the acetone molecule is greater than lo8 Hz even at the lowest temperature measured (84 K). Analytical expressions for the spin-lattice relaxation time (TI), for a twofold jump, were derived. Calculated values of the effective quadrupolar coupling constant and Tlmi, for the guests agree very well with the experimental data. The 84 K spectrum of acetone:TATM unexpectedly shows some asymmetry, the origin of which is discussed. Finally, these two clathrates are compared to the recently examined acetone:tri-ortho-thymotide inclusion compound.
Journal of Physical Chemistry B, May 23, 2003
ABSTRACT In the past few years, considerable effort has been put into the development of stable p... more ABSTRACT In the past few years, considerable effort has been put into the development of stable proton-conducting systems consisting of a strong acid dissolved in a solvent entrapped in a polymer gel. There has been continuing interest in orthophosphoric acid dissolved in aprotic solvents such as propylene carbonate (PC) and N,N-dimethyl formamide (DMF), which are contained in methacrylate-based polymer gels. In this report, we present the results of a study of those phosphoric acid−solvent−methacrylate-based polymer gel electrolytes that have ionic conductivities above 5 × 10-4 S·cm-1 at ambient temperature. FT-IR, FT-Raman, and high-resolution NMR spectroscopies are used. The objective is to understand better the interaction of orthophosphoric acid with the solvent and the polymer gel to gain information on possible proton-conduction mechanisms.
Review of Scientific Instruments, May 1, 1967
An asymmetrical rf bridge for pulsed magnetic resonance experiments is described. The balancing a... more An asymmetrical rf bridge for pulsed magnetic resonance experiments is described. The balancing adjustments, which can be made quickly and easily, ensure a proper impedance match to transmitter and receiver. The bridge is particularly well suited for pure nuclear quadrupole resonance experiments.
Inorganic Chemistry, Jun 1, 1976
Since the photoelectron spectrum of V(CO)6 indicates the ligand bonding molecular orbitals are at... more Since the photoelectron spectrum of V(CO)6 indicates the ligand bonding molecular orbitals are at least 5 eV lower in energy than are the metallike d orbitals,2b the charge-transfer bands are most likely transitions from the bzg and eg T* orbitals to the a2,, and e, Q* orbitals. The states expected for these one-electron transitions are listed in Table VII. Since only the two 2Eu states and the 2Blu states are electronic dipole allowed, these transitions are expected to give rise to the three strongest bands observed in the spectrum. Using this and the calculated d-orbital energies, tentative assignments for the charge-transfer spectrum have been made. The assignments for all of the observed electronic transitions of V(CO)6 are given in Table VIII. Conclusions As expected from previous studies, V(CO)6 was found to have D4h symmetry in matrices at low temperatures. The electronic spectrum of V(CO)6 in a CO matrix was examined and tentative assignments have been made for the bands contained in the spectrum. Approximate crystal field and Racah parameters have been determined. V2(C0)12 has been identified from the ir spectrum, and a tentative structure has been proposed for this molecule. Registry No. V(CO)6, 14024-00-1; V2(C0)12, 58815-50-2. References and Notes (1) Work performed for the U S. Energy Research and Development Administraction under Contract No. W-7405-eng-82 (2) (a) H.
Biophysical Journal, Sep 1, 1989
To understand 31P relaxation processes and hence molecular dynamics in the phospholipid multilaye... more To understand 31P relaxation processes and hence molecular dynamics in the phospholipid multilayer it is important to measure the dependence of the 31p spin-lattice relaxation time on as many variables as the physical system allows. Such measurements of the 31p spin-lattice relaxation rate have been reported both as a function of Larmor frequency and temperature for egg phosphatidylcholine liposomes (Milburn, M. P., and K. R. Jeffrey. 1987. Biophys. J. 52:791-799). In principle, the spin-lattice relaxation rate in an anisotropic environment such as a bilayer will be a function of the angle between the bilayer normal and the magnetic field. However, the measurement of this angular dependence has not been possible because the rapid (on the timescale of the spin-lattice relaxation rate) diffusion of the lipid molecules over the curved surface of the liposome average this dependence (Milburn, M.
Biochimica Et Biophysica Acta - Biomembranes, Aug 1, 1980
the same reduced temperature. Below 15°C a second component, due to gel phase lipid, starts to ap... more the same reduced temperature. Below 15°C a second component, due to gel phase lipid, starts to appear in the spectra. This broad gel phase component grows at the expense of the liquid crystal phase component as the temperature is reduced. The spectra indicate that the center of the phase transition is at about-12°C, in good agreement with DSC studies.
Chemistry and Physics of Lipids, Oct 1, 1977
Abstract Quadrupolar echo deuterium magnetic resonance spectroscopy is used to study the hydrocar... more Abstract Quadrupolar echo deuterium magnetic resonance spectroscopy is used to study the hydrocarbon chain disorder in a 70% potassium palmitate-30% water mixture. The CD bond order parameters are measured as a function of temperature and position along the chain. ...
Chemischer Informationsdienst, Sep 7, 1976
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Papers by Kenneth Jeffrey