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Spontaneous emission of NMR signals in hyperpolarized proton spin systems

Title
Spontaneous emission of NMR signals in hyperpolarized proton spin systems
Author
이영복
Keywords
Hyperpolarization; Radiation damping; NMR MASER; Spin temperature; Dynamic nuclear polarization
Issue Date
2011-02
Publisher
ACADEMIC PRESS INC ELSEVIER SCIENCE
Citation
JOURNAL OF MAGNETIC RESONANCE, v. 208, NO 2, Page. 204-209
Abstract
Hyperpolarization of nuclear spins is gaining increasing interest as a tool for improving the signal-to-noise ratio of NMR and MRI. While in principle, hyperpolarized samples are amenable to the same or similar experiments as are used in conventional NMR, the large spin polarization may give rise to unexpected effects. Here, spontaneous emission of signal was observed from proton spin systems, which were hyperpolarized to negative spin temperature by dynamic nuclear polarization (DNP). An unexpected feature of these emissions is that, without any radio-frequency excitation, multiple beats arise that cannot be explained by the Bloch equations with radiation damping. However, we show that a simple modification to these equations, which takes into account an additional supply of hyperpolarized magnetization from a reservoir outside of the active detection region, can phenomenologically describe the observed signal. The observed effect demonstrates that even well-known mechanisms of spin evolution can give rise to unexpected effects when working with hyperpolarized samples, which may need to be addressed through the development of new experimental techniques. (C) 2010 Elsevier Inc. All rights reserved.
URI
http://www.sciencedirect.com/science/article/pii/S1090780710003514?via%3Dihubhttp://hdl.handle.net/20.500.11754/35049
ISSN
1090-7807
DOI
10.1016/j.jmr.2010.11.002
Appears in Collections:
GRADUATE SCHOOL[S](대학원) > BIONANOTECHNOLOGY(바이오나노학과) > Articles
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