Exploiting adiabatically switched RF-field for manipulating spin hyperpolarization induced by parahydrogen

Abstract

A method for precise manipulation of non-thermal nuclear spin polarization by switching a RF-field is presented. The method harnesses adiabatic correlation of spin states in the rotating frame. A detailed theory behind the technique is outlined; examples of two-spin and three-spin systems prepared in a non-equilibrium state by Para-Hydrogen Induced Polarization (PHIP) are considered. We demonstrate that the method is suitable for converting the initial multiplet polarization of spins into net polarization: compensation of positive and negative lines in nuclear magnetic resonance spectra, which is detrimental when the spectral resolution is low, is avoided. Such a conversion is performed for real two-spin and three-spin systems polarized by means of PHIP. Potential applications of the presented technique are discussed for manipulating PHIP and its recent modification termed signal amplification by reversible exchange as well as for preparing and observing long-lived spin states.

SABRE Hyperpolarization of Bipyridine Stabilized Ir-Complex at High, Low and Ultralow Magnetic Fields

“…However, the observed polarization is anti-phase polarization, which can be a problem in practical applications (as the positive and negative NMR lines might cancel each other). Therefore to convert the anti-phase magnetization to in-phase magnetization we use a high-field method based on polarization transfer by adiabatic passage through an LAC; a similar technique was used before in PHIP [34]. Using an RF field, which is adiabatically switched off, one can convert the anti-phase spectrum to an in-phase one.…”

Metabolic Studies of Tumor Cells Using [1‐13C] Pyruvate Hyperpolarized by Means of PHIP‐Side Arm Hydrogenation

“…This chemistry‐based hyperpolarization method allows to obtain HP molecules following the catalytic hydrogenation of unsaturated substrates using hydrogen enriched in the para spin isomer, called para hydrogenation. Upon the chemical addition of the two parahydrogen protons to magnetically different sites, the spin order of parahydrogen can be converted into nuclear spin hyperpolarization, also thanks to the application of tailored spin order transfer (SOT) techniques . The need of an unsaturated precursor of the target hyperpolarized product, in which the parahydrogen protons are added at adjacent positions to the target heteronucleus, limited the application of this HP method to few metabolites (namely succinate and phospho‐lactate) .…”

13C MR Hyperpolarization of Lactate by Using ParaHydrogen and Metabolic Transformation in Vitro

“…Since 1 H-13 C isotropic mixing is achieved when ∆ −~− , the passage between strong to weak coupling that occurs during the adiabatic passage is achieved at lower magnetic field in the case of the allyl proton Ha in respect to the ethyl or methylene ones. Furthermore, for the adiabaticity criterion, [19] the minimal time compatible with adiabatic switching, for an AB two spin system, is roughly given by 1/JAB, therefore the remagnetization passage must be slowed down in order to facilitate the polarization transfer from the olefinic proton Ha to the target 13 C carboxylate. On this basis, the remagnetization step has been carried out between 25nT ( ∆ −~0 .8…”