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arXiv · 1802.00676

Spin-isomer conversion of water at room temperature, and quantum-rotor-induced nuclear polarization, in the water-endofullerene H$_2$O@C$_{60}$

Benno Meier·Karel Kouřil·Christian Bengs·Hana Kouřilová·Timothy J. Barker·Stuart J. Elliott·Shamim Alom·Richard J. Whitby·Malcolm H. Levitt
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Abstract

Water exists in two forms, para and ortho, that have nuclear spin states with different symmetries. Here we report the conversion of fullerene-encapsulated para-water to ortho-water. The enrichment of para-water at low temperatures is monitored via changes in the electrical polarizability of the material. Upon rapid dissolution of the material in toluene the excess para-water converts to ortho- water. In H$_2{}^{16}$O@C$_{60}$ the conversion leads to a slow increase in the NMR signal. In H$_2{}^{16}$O@C$_{60}$ the conversion gives rise to weak signal enhancements attributed to quantum-rotor-induced nuclear spin polarization. The time constants for the spin-isomer conversion of fullerene-encapsulated water in ambient temperature solution are estimated as 30$\pm$4 s for the $^{16}$O-isotopologue of water, and 16$\pm$3 s for the $^{17}$O isotopologue.

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Benno Meier, Karel Kouřil, Christian Bengs, Hana Kouřilová, Timothy J. Barker, Stuart J. Elliott, Shamim Alom, Richard J. Whitby, Malcolm H. Levitt. 2018-02-02. Spin-isomer conversion of water at room temperature, and quantum-rotor-induced nuclear polarization, in the water-endofullerene H$_2$O@C$_{60}$. https://doi.org/10.1103/physrevlett.120.266001

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