Parahydrogen
Parahydrogen is one of two magnetic forms of hydrogen gas (H2). It’s commonly used to increase the sensitivity of NMR and MRI measurements. Molecular hydrogen consists of two atoms. Each of the atoms has a spinning nucleus. Based on the direction of the nuclear spin, there are two types of hydrogens. If the spins of the two hydrogen nuclei are aligned, it’s orthohydrogen. If the spins are opposed, it’s parahydrogen. In general, hydrogens is an equilibrium mixture of ortho- and para-hydrogen. There is a tiny energy difference between the two magnetic states. Parahydrogen has the lowest energy. Therefore, to generate parahydrogen, it can be achieved by cooling hydrogen. A volume of hydrogen gas contains 75% orthohydrogen and 25% parahydrogen above room temperature, 50% orthohydrogen, and 50% parahydrogen at liquid nitrogen temperature, and 100% parahydrogen at 0K. A catalyst is also required to speed the conversion of orthohydrogen and parahydrogen in addition to the cryogenic temperature. It can be charcoal or iron oxide.
Customer References:
Jan-Bernd Hövener, Medical Physics, Department of Radiology, University Medical Center Freiburg, Germany: NMR Biomed., 26: 124-131 (2012).
Related Cryostats:
