Scientists at UC Berkeley, Lawrence Berkeley National Lab, and National Institute of Standards and Technology demonstrated the detection of nuclear magnetic resonance (NMR) signals without setting up a magnetic field at all. Not having to use powerful superconducting magnets in future NMR devices will allow them to be considerably smaller, more portable, cheaper, and safer.
PhysicsWorld explains:
First, the problem of spin coupling without an applied magnetic field can be overcome by employing a technique known as “parahydrogen-induced polarization”. Parahydrogen is a spin isomer form of hydrogen with the anti-parallel spin alignment, forming a “singlet state” (see image above). The technique used by them transfers a special kind of polarization from to the sample molecule, resulting in enormous signal enhancement. While the phenomenon of parahydrogen-induced polarization has been known for some time, the current work is the first to successfully use it in zero-field.
The researchers then used an innovative technique to measure the faint magnetic fields. The detectors used in early experiments with low-field NMR needed to be cooled to near absolute zero, which defeated the purpose of removing the applied field in the first place. Instead, the researchers modified a different type of detector called an “optical atomic magnetometer” – which requires no refrigeration – for use at zero-field.
Link @ PhysicsWorld: NMR spectroscopy without the ‘M’
Study abstract in Nature Physics: Parahydrogen-enhanced zero-field nuclear magnetic resonance