Development of Model-free Analysis Method on Quasi-elastic Neutron Scattering and Application to Liquid Water

Abstract

In general, analysis of quasi-elastic neutron scattering spectra needs some mathematical models in its process, and hence the obtained result is a model dependent. Model-dependent analysis may lead misunderstandings caused by inappropriate initial models or may miss an unexpected relaxation phenomenon. We have developed an analysis method for processing QENS data without a specific model, which we call as mode-distribution analysis. In this method, we supposed that all modes can be described as combinations of the relaxations based on the exponential law. By this method, we can obtain a distribution function B (Q, Γ) which we call the mode-distribution function, to represent the number of relaxation modes and distributions of the relaxation times in the modes. We report the first application to experimental data of liquid water. In addition to the two known modes, the existence of a relaxation mode of water molecules with an intermediate time scale has been discovered.