Dynamic Nuclear Polarization
Low signal-to-noise ratios are a challenge in NMR spectroscopy. You can boost signal NMR intensities with Dynamic Nuclear Polarization (DNP NMR). Bridge12 offers DNP upgrades for your new or existing NMR spectrometer.
Surface Enhanced NMR Spectroscopy by Dynamic Nuclear Polarization
A. Lesage et al., Surface enhanced NMR Spectroscopy by Dynamic Nuclear Polarization, J. Am. Chem. Soc., 2010, 132(44), 15459-15461
http://dx.doi.org/10.1021/ja104771z
It is shown that surface NMR spectra can be greatly enhanced using dynamic nuclear polarization. Polarization is transferred from the protons of the solvent to the rare nuclei (here carbon-13 at natural isotopic abundance) at the surface, yielding at least a 50-fold signal enhancement for surface species covalently incorporated into a silica framework.
Surface Enhanced NMR Spectroscopy by Dynamic Nuclear Polarization
A. Lesage et al., Surface enhanced NMR Spectroscopy by Dynamic Nuclear Polarization, J. Am. Chem. Soc., 2010, 132(44), 15459-15461
http://dx.doi.org/10.1021/ja104771z
It is shown that surface NMR spectra can be greatly enhanced using dynamic nuclear polarization. Polarization is transferred from the protons of the solvent to the rare nuclei (here carbon-13 at natural isotopic abundance) at the surface, yielding at least a 50-fold signal enhancement for surface species covalently incorporated into a silica framework.
High Field Dynamic Nuclear Polarization – The Renaissance
An entire issues dedicated to recent developments in high-field Dynamic Nuclear Polarization (DNP) and it\’s application to enhance NMR signal intensities published by the Royal Society of Chemistry (UK) in Physical Chemistry Chemical Physics, Issue 22.
High Field Dynamic Nuclear Polarization – The Renaissance
An entire issues dedicated to recent developments in high-field Dynamic Nuclear Polarization (DNP) and it\’s application to enhance NMR signal intensities published by the Royal Society of Chemistry (UK) in Physical Chemistry Chemical Physics, Issue 22.
Dynamic Nuclear Polarization in III–V Semiconductors
G. Kaur and G. Denninger, Dynamic Nuclear Polarization in III-V Semiconductors, Appl. Magn. Reson., 2010, 39(1-2), 185-204
http://dx.doi.org/10.1007/s00723-010-0155-7
We report on electron spin resonance, nuclear magnetic resonance and Overhauser shift experiments on two of the most commonly used III–V semiconductors, GaAs and InP. Localized electron centers in these semiconductors have extended wavefunctions and exhibit strong electron–nuclear hyperfine coupling with the nuclei in their vicinity. These interactions not only play a critical role in electron and nuclear spin relaxation mechanisms, but also result in transfer of spin polarization from the electron spin system to the nuclear spin system.
This transfer of polarization, known as dynamic nuclear polarization (DNP), may result in an enhancement of the nuclear spin polarization by several orders of magnitude under suitable conditions. We determine the critical range of doping concentration and temperature conducive to DNP effects by studying these semiconductors with varying doping concentration in a wide temperature range. We show that the electron spin system in undoped InP exhibits electric current-induced spin polarization. This is consistent with model predictions in zinc-blende semiconductors with strong spin–orbit effects.
Dynamic Nuclear Polarization in III–V Semiconductors
G. Kaur and G. Denninger, Dynamic Nuclear Polarization in III-V Semiconductors, Appl. Magn. Reson., 2010, 39(1-2), 185-204
http://dx.doi.org/10.1007/s00723-010-0155-7
We report on electron spin resonance, nuclear magnetic resonance and Overhauser shift experiments on two of the most commonly used III–V semiconductors, GaAs and InP. Localized electron centers in these semiconductors have extended wavefunctions and exhibit strong electron–nuclear hyperfine coupling with the nuclei in their vicinity. These interactions not only play a critical role in electron and nuclear spin relaxation mechanisms, but also result in transfer of spin polarization from the electron spin system to the nuclear spin system.
This transfer of polarization, known as dynamic nuclear polarization (DNP), may result in an enhancement of the nuclear spin polarization by several orders of magnitude under suitable conditions. We determine the critical range of doping concentration and temperature conducive to DNP effects by studying these semiconductors with varying doping concentration in a wide temperature range. We show that the electron spin system in undoped InP exhibits electric current-induced spin polarization. This is consistent with model predictions in zinc-blende semiconductors with strong spin–orbit effects.
Amplification of Picosecond Pulses in a 140-GHz Gyrotron-TravelingWave Tube
H.J. Kim et al., Amplification of Picosecond Pulses in a 140-GHz Gyrotron Travelling Wave Tube, Phys. Rev. Lett., 105(13), 135101-135104
http://dx.doi.org/10.1103/PhysRevLett.105.135101
An experimental study of picosecond pulse amplification in a gyrotron-traveling wave tube (gyro- TWT) has been carried out. The gyro-TWT operates with 30 dB of small signal gain near 140 GHz in the HE06 mode of a confocal waveguide. Picosecond pulses show broadening and transit time delay due to two distinct effects: the frequency dependence of the group velocity near cutoff and gain narrowing by the finite gain bandwidth of 1.2 GHz.
Experimental results taken over a wide range of parameters show good agreement with a theoretical model in the small signal gain regime. These results show that in order to limit the pulse broadening effect in gyrotron amplifiers, it is crucial to both choose an operating frequency at least several percent above the cutoff of the waveguide circuit and operate at the center of the gain spectrum with sufficient gain bandwidth.
Amplification of Picosecond Pulses in a 140-GHz Gyrotron-TravelingWave Tube
H.J. Kim et al., Amplification of Picosecond Pulses in a 140-GHz Gyrotron Travelling Wave Tube, Phys. Rev. Lett., 105(13), 135101-135104
http://dx.doi.org/10.1103/PhysRevLett.105.135101
An experimental study of picosecond pulse amplification in a gyrotron-traveling wave tube (gyro- TWT) has been carried out. The gyro-TWT operates with 30 dB of small signal gain near 140 GHz in the HE06 mode of a confocal waveguide. Picosecond pulses show broadening and transit time delay due to two distinct effects: the frequency dependence of the group velocity near cutoff and gain narrowing by the finite gain bandwidth of 1.2 GHz.
Experimental results taken over a wide range of parameters show good agreement with a theoretical model in the small signal gain regime. These results show that in order to limit the pulse broadening effect in gyrotron amplifiers, it is crucial to both choose an operating frequency at least several percent above the cutoff of the waveguide circuit and operate at the center of the gain spectrum with sufficient gain bandwidth.
Hyperpolarizing Gases via Dynamic Nuclear Polarization and Sublimation
A. Comment et al., Hyperpolarizing Gases via Dynamic Nuclear Polarization and Sublimation, Phys. Rev. Lett., 2010, 105(1), 018104-018107.
http://dx.doi.org/10.1103/PhysRevLett.105.018104
A high throughput method was designed to produce hyperpolarized gases by combining low temperature dynamic nuclear polarization with a sublimation procedure. It is illustrated by applications to 129Xe nuclear magnetic resonance in xenon gas, leading to a signal enhancement of 3 to 4 orders of magnitude compared to the room-temperature thermal equilibrium signal at 7.05 T.
Hyperpolarizing Gases via Dynamic Nuclear Polarization and Sublimation
A. Comment et al., Hyperpolarizing Gases via Dynamic Nuclear Polarization and Sublimation, Phys. Rev. Lett., 2010, 105(1), 018104-018107.
http://dx.doi.org/10.1103/PhysRevLett.105.018104
A high throughput method was designed to produce hyperpolarized gases by combining low temperature dynamic nuclear polarization with a sublimation procedure. It is illustrated by applications to 129Xe nuclear magnetic resonance in xenon gas, leading to a signal enhancement of 3 to 4 orders of magnitude compared to the room-temperature thermal equilibrium signal at 7.05 T.