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Publication Citation: Probing the paramagnetic interactions between the unpaired electronic spins of carbon atoms and the nuclear spins of hydrogen molecules with Raman spectroscopy

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Author(s): Andrea Centrone;
Title: Probing the paramagnetic interactions between the unpaired electronic spins of carbon atoms and the nuclear spins of hydrogen molecules with Raman spectroscopy
Published: December 01, 2011
Abstract: Carbon materials typically have a high density of unpaired electronic spins but the exact nature of the defect sites that give rise to their magnetic properties are not yet well understood. In this work, the paramagnetic interactions between the unpaired electronic spins of carbon atoms and the nuclear spins of hydrogen molecules were probed with Raman spectroscopy by monitoring the relative population of H2 rotational states. For H2, the symmetries of nuclear spin and rotational wave functions are correlated. Because of the weak interactions between H2 nuclear spins, the transitions between odd and even rotational states are normally hindered. The magnetic field generated by unpaired electronic spins relaxes the selection rules and promotes transitions between H2 rotational levels of different symmetry. This affects the rotational levels relaxation kinetics toward equilibrium and makes H2 molecules useful to study unpaired electrons in paramagnetic materials. It is suggested that simultaneous EPR and Raman measures on carbon materials interacting with hydrogen molecules could result in a better understanding of the nature of paramagnetic defects in carbon materials, which could have a substantial impact on Li-ion batteries or for understanding the graphene electronic properties.
Citation: Journal of Raman Spectroscopy
Volume: 42
Issue: 12
Pages: pp. 2165 - 2167
Keywords: Raman Spectroscopy; Carbon Materials, Electron Paramagnetic Resonance
Research Areas: Characterization, Nanometrology, and Nanoscale Measurements, Materials Science, Molecular Spectroscopy
PDF version: PDF Document Click here to retrieve PDF version of paper (444KB)