Raman microprobe polarization measurements as a tool for studying the structure and orientation of molecules and clusters incorporated into cubic zeolites: S_8 and Se_(12) rings in zeolite A

摘要

Raman spectra of molecules or clusters incorporated into cubic zeolites are usually studied us microcrystalline powder samples, light being completely unpolarized because of multiple reflect on microcrystal surfaces. Therefore, all information about symmetry of the Raman-active vibrati, of species and orientation of species in zeolite cavities is lost. In order to save this information, , propose to do Raman microprobe polarization measurements of cubic zeolite single CrySI containing examined species: We theoretically consider examples of high-symmetry anisotro species (planelike or rodlike molecules or clusters with the threefold or higher major ~ incorporated into cubic zeolite A. We experimentally study polarization and angular dependen< of Raman spectra of S8 and Sel2 rings incorporated into zeolite A single crystal. The obtail dependencies correspond to the C4u point group symmetry S8rings oriented by their fourfold a along the fourfold axes of zeolite and th~ D3d point group symmetry Sel2 rings oriented by ti threefold axes along the threefold axes o(zeolite. The method applied to the S8 and Sel2 ring: considered as a new powerful tool for studying the structure and orientation of a wide class cubic-zeolite-confined species.