Nuclear Spin Relaxation in Gases

The sensitivity of conventional nuclear magnetic resonance (NMR) is rather poor compared with other spectroscopic techniques like EPR or optical spectroscopy. This is a result of the small population difference between the nuclear Zeeman energy levels even in the highest magnetic fields currently available in the laboratory. At room temperature, and in a magnetic field of 9.4 T, the polarisation of the protons is less than 4 x 10. In order to overcome this inherent limitation, methods to improve the signal to noise ratio (SNR) in magnetic resonance experiments have been the subject of active research since the discovery of NMR. 

Recently, several excellent reviews have appeared in the literature, discussing the use of hyperpolarized Xe from different perspectives. Cherubini and Bifone surveyed experiments involving hyperpolarized Xe and its biological applications, both in vitro and in vivo. Particular emphasis was put on the physico-chemical properties of xenon that are responsible for the interesting range of interactions with proteins, lipids and other biological materials. 

Han et visualized the melting and dissolution processes of xenon ice into 

Ishikawa et detected the free-induction signals of xenon atoms polarized by spin-exchange optical pumping. The temperature dependence of dissolution and spin-polarization transfer of xenon atoms in ethanol is measured by simultaneous detection of both xenon and ethanol protons. 

Polarization transfer from hyperpolarized gas to H, etc. holds great promise for sensitivity enhancement of solution-state NMR. Leawoods et al.  

The large diffusion coefficient of gases result in significant spin motion during the application of gradient pulses that typically last a few milliseconds in most NMR experiments. In restricted environments, such as the lung, this rapid gas diffusion can lead to violation of the narrow pulse approximation, a basic assumption of the standard Stejskal-Tanner method of diffusion measurements. Mair et therefore investigated the effect of a common, 

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Gordon R. G. Kinetic theory of nuclear spin relaxation in gases, J. Chem. Phys. 44, 228-34 (1966). 

Nuclear Spin Relaxation in Liquids and Gases 5 Self-diffusion in Liquids... 

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