Direct measurements of quantum kinetic energy tensor in stable and metastable water near the triple point: an experimental benchmark

摘要

This study presents the first direct and quantitative measurements of thenuclear momentum distribution anisotropy and the quantum kinetic energy tensorin stable and metastable (supercooled) water near its triple point using DeepInelastic Neutron Scattering (DINS). From the experimental spectra accuratelineshapes of the hydrogen momentum distributions are derived using ananisotropic Gaussian and a model independent framework. The experimentalresults, benchmarked with those obtained for the solid phase, provide the stateof the art directional values of the hydrogen mean kinetic energy in metastablewater. The determinations of the direction kinetic energies in the supercooledphase, benchmarked with ice at the same temperature, provide accurate andquantitative measurements of these dynamical observables in metastable andstable phases, {i.e.} key insight in the physical mechanisms of the hydrogenquantum state in both disordered and polycrystalline systems. The remarkablefindings of this study establish novel insight to further expand the capacityand accuracy of DINS investigations of the nuclear quantum effects in water andrepresent reference experimental values for theoretical investigations.