Vibrational Multipolar Analyses in Isotropic Media: Combining IR, Raman and Hyper-Raman Spectroscopies

摘要

We introduce combined vibrational multipolar decompositions of IR, polarized Raman and hyper-Raman spectra as a powerful way to study isotropic materials. This new procedure has been applied to the molecular liquid HCCl_3 and to silica glass, which are made of elementary structural units (ESU) weakly interacting and covalently 3D-linked, respectively. Through the vibrational multipolar analyses of these two different isotropic media, new structural and dynamical insights have been drawn. In particular, for silica we propose an ESU which fits the multipolar spectral activity. It is derived from the α-Cristoballite structure, with an octupolar S_4 symmetry, which consists of a central SiO_4 tetrahedron embedded in a super Si_(4/4) tetrahedron with bent Si-O-Si bonds.