R.D Kendrick

Magnetic resonance force detection and spectroscopy of electron spins in phosphorus-doped silicon

Electron spin resonance (ESR) of phosphorus-doped silicon was detected using a low temperature magnetic resonance force microscope (MRFM). Force-detected ESR spectra were obtained using an amplitude or frequency modulated microwave field to cyclically saturate the spin magnetization. For a sample containing 4×1018 phosphorus atoms/cm3, a single strong ESR line was observed. For a sample containing 8×1016 phosphorus atoms/cm3, a pair of lines split by the 42 G 31P hyperfine interaction was observed. This result demonstrates the possibility of using MRFM techniques for spectroscopic purposes.

Cross polarization magic-angle spinning NMR at cryogenic temperatures

Abstract A magic angle spinning (MAS) apparatus which can be used for high resolution solid state NMR at temperatures as low as 15 K is described. To demonstrate the utility of this apparatus, 13 C spectra of molecules containing methyl groups have been investigated at cryogenic temperatures. The spectra, which are described in detail, provide direct evidence for the slowdown of methyl rotation.

High‐temperature NMR using inductive heating

We report a simple, efficient method for carrying out nuclear magnetic resonance (NMR) experiments at high temperature in any NMR probe without modification. The sample tube is coated with a thin film of metal and the rf coil used for the NMR experiment is used to inductively heat the film, thus heating the sample inside the tube. Using this approach, we have obtained both proton and high‐resolution carbon‐13 NMR spectra at temperatures as high as 730 K.

Dynamic nuclear polarization via confined electrons in bulk solids

Abstract Nuclear polarization dynamics arising from saturation of the EPR of an electron-rich component of a composite polymer material are reported. The unpaired electrons are confined to islands of polyacetylene embedded in a matrix of polyethylene. The interaction among the three kinds of spin in the sample (unpaired electrons, 13C, and 1H, their natural abundance, and the fact that the electrons are confined to small regions of the sample lead to a rich variety of spin dynamics constituting a solid-state analog of the “three-spin” effect discovered in solution DNP studies several years ago.

Molecular Structure and Dynamics in Organic Solids: High Resolution Low Temperature 13 C NMR Studies

Abstract The development of cross polarization-magic angle spinning (CPMAS) has resulted in the achievement of near-liquid resolution in solid state 13 C NMR spectra. Therefore, the structure and dynamics of organic solids can now be studied on a carbon-by-carbon basis. Low temperature CPMAS capability permits the investigation of molecular dynamics in solids, and in particular in a temperature range heretofore inaccessible to high resolution NMR (15-200 K). We have developed and used low temperature CPMAS to study solid state effects on chemical exchange processes in organic and organometallic compounds and in carbonium ions. We have also developed a technique for measuring carbon-carbon bond lengths in amorphous solids using NMR. The geometry of cis-and trans-polyacetylene has been determined using this method.