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Hyperpolarization (physics)
Hyperpolarization is the nuclear spin polarization of a material far beyond thermal equilibrium conditions. It is commonly applied to gases such as 129Xe and 3He, where the polarization levels can be enhanced by a factor of 104-105 above thermal equilibrium levels. Hyperpolarized noble gases are typically used in magnetic resonance imaging (MRI) of the lungs.
==Spin-Exchange Optical Pumping==
3He and 129Xe are generally hyperpolarized using a process called spin-exchange optical pumping (SEOP). During this process, circularly polarized infrared laser light, tuned to the appropriate wavelength, is used to excite electrons in an alkali metal, such as caesium or rubidium inside a sealed glass vessel. The angular momentum is transferred from the alkali metal electrons to the noble gas nuclei through collisions. Nitrogen is used as a quenching gas, which prevents the fluorescence of the polarized alkali metal, which would lead to de-polarization of the noble gas. Great improvements in 129Xe hyperpolarization technology have achieved > 50% level at flow rates of 1–2 L/min, which enables human clinical applications.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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