Real time and real space analysis for coherent QENS and its application to liquid bismuth

コヒーレントQENSに対する実時間実空間解析と液体ビスマスへの応用

菊地 龍弥*  ; 川北 至信  

Kikuchi, Tatsuya*; Kawakita, Yukinobu

Real time and real space analysis for quasielastic neutron scattering (QENS) by means of the regularization method to estimate a spectrum has been developed. In our formalism, a mediation function between a dynamic structure factor, , and a time-space correlation function, ,is estimated to minimize the sum of the least square fitting term for in a space and the regularization term for in a space. On the application to liquid bismuth which shows complicate static local structure, it is shown that a distribution function for Gaussian superposition to represent has good characters as a mediating function. The calculated from the estimated mediation function showed a good agreement with the experimental even for small acoustic phonon excitation in a low region and gave more or less reasonable estimation of dynamic structure beyond the measured range. In addition of the main property of that the ability to focus onto the relaxation process at a specific atomic distance helped us to understand a complicated layered structure in liquid bismuth, possibility of easy separation of self-diffusion from coherent QENS is shown.