Heteronuclear polarization transfer in static oriented systems using a windowless multiple-pulse sequence

A theory of the spin-lattice and spin-spin relaxation processes in quadrupole spin systems with I > 1/2 in the situation of the multiple-pulse NQR spin locking is proposed for the pulse sequence MW-4. The theory is based on the assumption that for t ≳ T2 the change of the spin system is a quasi-equilibrium process. Rate equations for inverse generalized temperatures are obtained and the kinetic coefficients calculated for the case o f exponential correlation functions. The above assumption was confirmed for some substances containing the 35Cl and 123Sb, and the time constant T1e characterizing the spin echo signal decay was investigated and compared with the time constant T1q, in the case of continuous spin locking.

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Boosting Dissolution-Dynamic Nuclear Polarization by Multiple-Step Dipolar Order Mediated 1H->13C Cross-Polarization

10.26434/chemrxiv.14377046 ◽

2021 ◽

Author(s):

Stuart J. Elliott ◽

Olivier Cala ◽

Quentin Chappuis ◽

Samuel Cousin ◽

Morgan Ceillier ◽

...

Keyword(s):

Dynamic Nuclear Polarization ◽

Nuclear Polarization ◽

Pulse Sequence ◽

Polarization Transfer ◽

Cross Polarization ◽

Spin Order ◽

Sample Dissolution ◽

Dipolar Order ◽

Multiple Step ◽

Dissolution Dynamic Nuclear Polarization

Dissolution-dynamic nuclear polarization can be boosted by employing multiplecontact cross-polarization techniques to transfer polarization from 1H to 13C spins. The method is efficient and significantly reduces polarization build-up times, however, it involves high-power radiofrequency pulses in a superfluid helium environment which limit its implementation and applicability and prevent a significant scaling-up of the sample size. We propose to overcome this limitation by a stepwise transfer of polarization using a lowenergy and low-peak power radiofrequency pulse sequence where the 1H®13C polarization transfer is mediated by a dipolar spin order reservoir. An experimental demonstration is presented for [1-13C]sodium acetate. A solid-state 13C polarization of ~43.5% was achieved using this method with a build-up time constant of ~5.1 minutes, leading to a ~28.5% 13C polarization in the liquidstate after sample dissolution. The low-power multiple-step polarization transfer efficiency with respect to the most advanced and highest-power multiple-contact cross-polarization approach was found to be ~0.69.

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Boosting Dissolution-Dynamic Nuclear Polarization by Multiple-Step Dipolar Order Mediated 1H->13C Cross-Polarization

10.26434/chemrxiv.14377046.v1 ◽

2021 ◽

Author(s):

Stuart J. Elliott ◽

Olivier Cala ◽

Quentin Chappuis ◽

Samuel Cousin ◽

Morgan Ceillier ◽

...

Keyword(s):

Dynamic Nuclear Polarization ◽

Nuclear Polarization ◽

Pulse Sequence ◽

Polarization Transfer ◽

Cross Polarization ◽

Spin Order ◽

Sample Dissolution ◽

Dipolar Order ◽

Multiple Step ◽

Dissolution Dynamic Nuclear Polarization

Dissolution-dynamic nuclear polarization can be boosted by employing multiplecontact cross-polarization techniques to transfer polarization from 1H to 13C spins. The method is efficient and significantly reduces polarization build-up times, however, it involves high-power radiofrequency pulses in a superfluid helium environment which limit its implementation and applicability and prevent a significant scaling-up of the sample size. We propose to overcome this limitation by a stepwise transfer of polarization using a lowenergy and low-peak power radiofrequency pulse sequence where the 1H®13C polarization transfer is mediated by a dipolar spin order reservoir. An experimental demonstration is presented for [1-13C]sodium acetate. A solid-state 13C polarization of ~43.5% was achieved using this method with a build-up time constant of ~5.1 minutes, leading to a ~28.5% 13C polarization in the liquidstate after sample dissolution. The low-power multiple-step polarization transfer efficiency with respect to the most advanced and highest-power multiple-contact cross-polarization approach was found to be ~0.69.

Download Full-text