Model for the rotational contribution to quasielastic neutron scattering spectra from supercooled water

A model is proposed for the first-, second-, and third-order rotational correlation functions that are required for the computation of the rotational intermediate scattering function for the calculation of incoherent quasielastic neutron scattering (QENS) spectra from supercooled water. The model is tested against molecular-dynamics data generated from an extended-simple-point-charge model of water and is found to be satisfactory. The model can be used as a practical method for extracting rotational relaxation parameters from QENS spectra measured at large Q from supercooled bulk water or interfacial water in porous materials.