Category Archives: Haupt Effect

Long-lived nuclear spin states in methyl groups and quantum-rotor-induced polarization

Meier, B., et al., Long-lived nuclear spin states in methyl groups and quantum-rotor-induced polarization. J Am Chem Soc, 2013. 135(50): p. 18746-9.

http://www.ncbi.nlm.nih.gov/pubmed/24252212

Substances containing rapidly rotating methyl groups may exhibit long-lived states (LLSs) in solution, with relaxation times substantially longer than the conventional spin-lattice relaxation time T1. The states become long-lived through rapid internal rotation of the CH3 group, which imposes an approximate symmetry on the fluctuating nuclear spin interactions. In the case of very low CH3 rotational barriers, a hyperpolarized LLS is populated by thermal equilibration at liquid helium temperature. Following dissolution, cross-relaxation of the hyperpolarized LLS, induced by heteronuclear dipolar couplings, generates strongly enhanced antiphase NMR signals. This mechanism explains the NMR signal enhancements observed for (13)C-gamma-picoline (Icker, M.; Berger, S. J. Magn. Reson. 2012, 219, 1-3).

Transfer of the Haupt-hyperpolarization to neighbor spins

Icker, M., P. Fricke, and S. Berger, Transfer of the Haupt-hyperpolarization to neighbor spins. J. Magn. Reson., 2012. 223(0): p. 148-150.

http://dx.doi.org/10.1016/j.jmr.2012.07.019

The NMR hyperpolarization observed for freely rotating methyl groups by exerting a temperature jump from 4.2 K to 298 K can be transferred to spins which have a spin, spin coupling with the carbon of the methyl group. First, a spin echo sequence readjusts the primary up/down signals to an in-phase multiplet. This in-phase magnetization is then decoupled and transferred by a simple COSY step using one scan. The polarization factors at the neighbor spins are about 50 by comparing their signal-to-noise ratio with the signal strength after full relaxation.

Transfer of the Haupt-hyperpolarization to neighbor spins

Icker, M., P. Fricke, and S. Berger, Transfer of the Haupt-hyperpolarization to neighbor spins. J. Magn. Reson., 2012. 223(0): p. 148-150.

http://dx.doi.org/10.1016/j.jmr.2012.07.019

The NMR hyperpolarization observed for freely rotating methyl groups by exerting a temperature jump from 4.2 K to 298 K can be transferred to spins which have a spin, spin coupling with the carbon of the methyl group. First, a spin echo sequence readjusts the primary up/down signals to an in-phase multiplet. This in-phase magnetization is then decoupled and transferred by a simple COSY step using one scan. The polarization factors at the neighbor spins are about 50 by comparing their signal-to-noise ratio with the signal strength after full relaxation.

Unexpected multiplet patterns induced by the Haupt-effect

This article is not about microwave driven DNP, however, similar effects that can be attributed to the Haupt Effect have been already observed in dissolution-DNP.

Icker, M. and S. Berger, Unexpected multiplet patterns induced by the Haupt-effect. J. Magn. Reson., 2012. 219(0): p. 1-3.

http://dx.doi.org/10.1016/j.jmr.2012.03.021

An NMR polarization up to a factor of 100 compared to the room temperature signal of a fully equilibrated sample and up/down multiplets are observed when 4-methyl-pyridine or toluene are taken rapidly from liquid helium temperatures to room temperature by dissolving in acetone-d6. These findings result from the inherent coupling between rotational and nuclear spin states in methyl groups which can act as quantum rotors. The temperature jump causes changes in rotational and spin energy level population due to symmetry rules that is known as the Haupt-effect.

Unexpected multiplet patterns induced by the Haupt-effect

This article is not about microwave driven DNP, however, similar effects that can be attributed to the Haupt Effect have been already observed in dissolution-DNP.

Icker, M. and S. Berger, Unexpected multiplet patterns induced by the Haupt-effect. J. Magn. Reson., 2012. 219(0): p. 1-3.

http://dx.doi.org/10.1016/j.jmr.2012.03.021

An NMR polarization up to a factor of 100 compared to the room temperature signal of a fully equilibrated sample and up/down multiplets are observed when 4-methyl-pyridine or toluene are taken rapidly from liquid helium temperatures to room temperature by dissolving in acetone-d6. These findings result from the inherent coupling between rotational and nuclear spin states in methyl groups which can act as quantum rotors. The temperature jump causes changes in rotational and spin energy level population due to symmetry rules that is known as the Haupt-effect.

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