Inelastic nuclear resonant scattering and its application to tin materials.

摘要

In this thesis we present a study of a new experimental technique, the inelastic nuclear resonant scattering (INRS), and particularly its application to investigate lattice dynamics in tin-containing materials. The advances in synchrotron radiation and X-ray optics make this technique possible. It is a unique method to investigate vibrational dynamics and is complementary to other well established experimental techniques. It has element, or more precisely, isotope selectivity as its most unique feature. It is able to provide energy spectrum of vibrational modes as well as integrated lattice vibrational properties, such as the recoilless factor and mean kinetic energy per atom. It works with small amount of materials, so is suitable to study thin films, interfaces, and samples under artificial high pressure. A detailed study of INRS in general is given in the first chapter, where we start with nuclear resonant cross section to explain what is measured in such experiments. Then data analysis procedure is described for extracting information from measured spectra. Count rate estimate is also given for establishing the feasibility and planning of experiments. The monochromator development at its resonant energy 23.88 keV is a necessary and important part of realizing INRS experiments for 119Sn. By extending the design of high resolution monochromator at lower energy, we have developed the capability of 1 meV resolution for 24 keV X-rays. A description of the monochromators and their operation is given in Chapter 3. Then we discuss results of INRS measurements of several tin materials and compounds. Finally, we point out a few future developments and applications in the last chapter.