When water is confined to nanocavities, its quantum-mechanical behavior can be revealed by terahertz spectroscopy. We place H2O molecules in the nanopores of a beryl crystal-lattice and observe a rich and highly anisotropic set of absorption lines in the terahertz spectral range. Two bands can be identified, which originate from translational and librational motions of the water molecule isolated within the cage; they correspond to the analogous broad bands in liquid water and ice. In the present case of well-defined and highly symmetric nanocavities, the observed fine structure can be explained by macroscopic tunneling of the H2O molecules within a six-fold potential caused by the interaction of the molecule with the cavity walls.
@article{arxiv.1310.6687,
title = {Quantum Behavior of Water Molecules Confined to Nanocavities in Gemstone},
author = {Boris P. Gorshunov and Elena S. Zhukova and Victor I. Torgashev and Vladimir V. Lebedev and Gilman S. Shakurov and Reinhard K. Kremer and Efim V. Pestrjakov and Victor G. Thomas and Dimitry A. Fursenko and Martin Dressel},
journal= {arXiv preprint arXiv:1310.6687},
year = {2013}
}