Vive la Différence! (APS Physics)

Feb 18, 2014
Lucio Frydman, Department of Chemical Physics, Weizmann Institute of Sciences, 76100 Rehovot, Israel
Published February 18, 2014  |  Physics 7, 17 (2014)  |  DOI: 10.1103/Physics.7.17

Long-lived singlet states—zero-spin states made of two spin - 1/2 particles—can be created by combining two different atomic species such as carbon and hydrogen.

Where would we be without singlet states? Almost all molecules in nature—and in our bodies—exist as singlet states, which arise when two particles with a spin of 1/2 combine into an eigenstate with zero spin. Their most common occurrence is in stable atomic or molecular orbitals. Their combination into a spinless state frees the pair from angular/magnetic momenta, leading to a particularly stable diamagnetic combination. Because they don’t have a net magnetic moment, singlets are long-lived states. This is a property with important practical implications for nuclear magnetic resonance (NMR): although singlets are not directly measurable in NMR, their long lifetime can be exploited to enhance the sensitivity of NMR experiments and extend the range of dynamic phenomena that NMR can probe [in either its spectroscopic (NMR) or imaging (MRI) modes].

A sine qua non condition for creating such singlet states is that its constituents be identical—or at least so we believed. But now, a study in Physical Review Letters by Meike Emondts from RWTH Aachen University, Germany, and co-workers demonstrates a singletlike state made of two different spin- 1/2 particles: a hydrogen nucleus and a bonded carbon-13 counterpart [1]. Evidence for the singlet nature of the state they construct is given by the long lifetime of this state, which exceeds the lifetime of either atom by a factor of 3. The demonstration of heteronuclear singlets thus challenges theoretical preconceptions and dramatically extends the range of systems that can be potentially probed via enhanced forms of singlet-state-based NMR.


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About the Author: Lucio Frydman

Frydman earned a Ph.D. in physical chemistry (1990) from the University of Buenos Aires. In 1992, after a postdoc at the University of California, Berkeley, he became professor in the Department of Chemistry of the University of Illinois in Chicago. In 2001, he moved to Israel to become professor at the Weizmann Institute, where he currently works in the Department of Chemical Physics. In 2012, Frydman became the director of the Helen L. and Martin S. Kimmel Institute for Magnetic Resonance, and chief scientist in chemistry and biology at the U.S. National High Magnetic Field Lab. Frydman’s research focuses on magnetic resonance spectroscopy and imaging in solids, liquids, and under in vivo conditions.

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