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Relaxation of longitudinal and singlet nuclear spin order as a function of solvent viscosity

Relaxation of longitudinal and singlet nuclear spin order as a function of solvent viscosity
Relaxation of longitudinal and singlet nuclear spin order as a function of solvent viscosity
Extending the storage time of nuclear spin order is an important issue in modern NMR spectroscopy since many NMR and MRI applications are limited by the lifetime of spin states. Under normal circumstances the survival of spin magnetization is limited by longitudinal relaxation (T1) which brings the magnetization back to equilibrium within a few seconds. The conversion of longitudinal into singlet order can extend that lifetime to tens of minutes up to an hour.
Most nuclear spin relaxation mechanisms in liquids are a function of the correlation time τc of the molecule, which is linked to the molecular tumbling, and inversely proportional to viscosity. Therefore a lower viscosity would reduce the influence of those mechanisms. The increase in the lifetime of longitudinal (T1) and singlet order (TS) is shown here as the viscosity of common organic solvents decreases.
The study includes measurements in liquid and supercritical CO2, that offer an extremely low viscosity regime. The further extension of spin order lifetimes for a singlet bearing molecule in liquid CO2 is presented. There appears to be an upper limit to the extension of the singlet order lifetime that is caused by relaxation mechanisms acting in different directions.
University of Southampton
Moysiadi, Aliki
46fd11f7-a435-4f8e-83d7-5c9e3d98a737
Moysiadi, Aliki
46fd11f7-a435-4f8e-83d7-5c9e3d98a737
Pileio, Giuseppe
13f78e66-0707-4438-b9c9-6dbd3eb7d4e8

Moysiadi, Aliki (2018) Relaxation of longitudinal and singlet nuclear spin order as a function of solvent viscosity. University of Southampton, Doctoral Thesis, 88pp.

Record type: Thesis (Doctoral)

Abstract

Extending the storage time of nuclear spin order is an important issue in modern NMR spectroscopy since many NMR and MRI applications are limited by the lifetime of spin states. Under normal circumstances the survival of spin magnetization is limited by longitudinal relaxation (T1) which brings the magnetization back to equilibrium within a few seconds. The conversion of longitudinal into singlet order can extend that lifetime to tens of minutes up to an hour.
Most nuclear spin relaxation mechanisms in liquids are a function of the correlation time τc of the molecule, which is linked to the molecular tumbling, and inversely proportional to viscosity. Therefore a lower viscosity would reduce the influence of those mechanisms. The increase in the lifetime of longitudinal (T1) and singlet order (TS) is shown here as the viscosity of common organic solvents decreases.
The study includes measurements in liquid and supercritical CO2, that offer an extremely low viscosity regime. The further extension of spin order lifetimes for a singlet bearing molecule in liquid CO2 is presented. There appears to be an upper limit to the extension of the singlet order lifetime that is caused by relaxation mechanisms acting in different directions.

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Moysiadi MPhil Thesis - Version of Record
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Published date: June 2018

Identifiers

Local EPrints ID: 425870
URI: http://eprints.soton.ac.uk/id/eprint/425870
PURE UUID: 052424de-f006-4bcf-b69c-f04f50bb2d2a
ORCID for Giuseppe Pileio: ORCID iD orcid.org/0000-0001-9223-3896

Catalogue record

Date deposited: 05 Nov 2018 17:30
Last modified: 24 Sep 2021 04:01

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Contributors

Author: Aliki Moysiadi
Thesis advisor: Giuseppe Pileio ORCID iD

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