Giving NMR A Signal Boost

Scientists have modified the nuclear magnetic resonance method to collect light signals in addition to radio signals, thus broadening the utility of the technology.

AsianScientist (Feb. 6, 2018) – An international team of scientists led by Japanese researchers Dr. Kazuyuki Takeda of Kyoto University and Associate Professor Koji Usami of the University of Tokyo has developed a method to convert nuclear magnetic resonance (NMR) radio signals into light signals. They published their findings in Optica.

NMR is a branch of spectroscopy where scientists measure the spin of an atom’s nucleus in order to determine its identity. Atomic nuclei subjected to a magnetic field induce radio frequency signals in a detector circuit. Since different atoms cause signals at different frequencies, scientists can use this information to determine the compounds contained in a sample. The most well-known application of this is in MRI-based imagining, such as CT scans.

“NMR is a very powerful tool, but its measurements rely on amplification of electrical signals at radio-frequencies. That pulls in extra noise and limits the sensitivity of our measurements,” said Takeda. “So we developed an experimental NMR system from scratch, which converts radio-frequency signals into optical ones.”

Their detection method relies on up-converting radio signals into light signals and has the potential to provide more sensitive analysis compared with conventional NMR. The principle behind this up-conversion is a hybrid quantum conversion technology which connects electronics to mechanics, and then to optics. The material linking all three systems is an elastic membrane of silicon nitride.

“We constructed a capacitor by vacuum-depositing a metal layer onto the silicon nitride membrane,” explained co-author Usami. “Using this with an inductor, we built a resonator to detect NMR signals, and next constructed an optical cavity using the metal layer as a mirror. The incoming electric NMR signal shakes the membrane, causing motion that is detected by an optical interferometer.”

The team believes that the success of this optical detection can broaden the usefulness of NMR spectroscopy, with the hope that this increased accuracy in detection and characterization of materials can be utilized in multiple scientific disciplines.

“Various methods for optical NMR detection have been reported, and while some are highly sensitive, they have so far lacked widespread applicability. Our new scheme has proven to be both versatile and applicable to a wide range of materials,” said Takeda.

The article can be found at: Takeda et al. (2018) Electro-mechano-optical Detection of Nuclear Magnetic Resonance.


Source: Kyoto University; Photo: Kazuyuki Takeda.
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