Berlin 2015 – wissenschaftliches Programm

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BP: Fachverband Biologische Physik

BP 11: Nanoparticles and Composite Materials II (joint CPP/BP)

BP 11.13: Vortrag

Montag, 16. März 2015, 18:15–18:30, C 243

Electric detection of ortho and para water in fullerene cages — •Benno Meier, Salvatore Mamone, Javier Alonso-Valdesueiro, Maria Concistrè, Andrea Krachmalnicoff, Richard J. Whitby, and Malcolm H. Levitt — School of Chemistry, University of Southampton, SO17 1BJ Southampton, United Kingdom

Water, like molecular hydrogen, exhibits spin isomerism, a phenomenon in which the entanglement of spatial and spin states leads to ortho and para spin isomers with different symmetry. The physical properties and the interconversion of the two isomers of molecular hydrogen are central to fields as diverse as astrophysics and nuclear magnetic resonance, but much remains unknown about the different isomers of water, owing to the difficulty of separating the two isomers. Here, we use fullerene cages to provide freely rotating water molecules at cryogenic temperatures in the form of the supramolecular endofullerene H2O@C60. Unlike molecular hydrogen, water has an electric dipole moment and we show that the dielectric constant, a bulk property, that is linked to the spin states via their molecular polarizabilities, changes upon ortho-para conversion that is induced by a sudden temperature change. Our findings are in excellent agreement with previous NMR studies and suggest the possibility to detect and eventually manipulate H2O@C60 molecules selectively depending on the nuclear spin state of the comprised water molecule.