Data Analysis And Model Comparison Based On Quasi-elastic Neutron Scattering Spectra

The Quasi-Elastic Neutron Scattering(QENS)experiment is a valuable method for studying dynamics of water.The commonly used neutron spectrometers are Time-of-flight spectrometer,Backscattering spectrometer and Neutron spin echo.The energy resolution of QENS spectra measured by different spectrometers varies from meV to μeV.When QENS spectra with different energy resolution are fitted by using a model,the fitted effect and the extracted parameters may be different.For example,if a model suits to fit QENS spectra with low energy resolution,it may not be suitable for high energy resolution.Our goal is to test whether the simple revised Jumpdiffusion and Rotation-diffusion Model(srJRM),which has shown a good performance in fitting QENS spectra with high energy resolution,is suitable to fit QENS spectra with low energy resolution.At first,three models are used to fit the QENS spectra from montmorillonite,which are the Double-Lorentzian Model(DLM),Jump-diffusion and Rotation-diffusion Model(JRM),and srJRM.The energy resolution of the QENS spectra is 30 μeV treated as low energy resolution.The fitting results show that the three models are good in the QENS spectra fit,and the extracted parameters can provide information of the immobile water and the dynamics of mobile water contained in samples.And then,srJRM is used to fit the QENS spectrum of MSH(Magnesium Silicate Hydrate)cement sample with relatively high energy resolution(3.5 μeV).It shown that the srJRM can fit the QENS data better than the JRM;Compared with the revised JRM,the srJRM has fewer fitted parameters,and the fitted parameter values are more consistent with other relevant studies.It can be seen that srJRM is a better model for fitting QENS spectrum data with both high energy resolution and low energy resolution.