Relevance of the electric-dipole--electric-quadrupole contribution to Raman optical activity spectra

We examine the importance of the electric-dipole--electric-quadrupole polarizability tensor in the intensity theory of Raman optical activity (ROA) spectra. Using density functional theory, ROA spectra of organic cyclic compounds, alanine, oligoalanines, and examples from the literature are analyzed in detail, and a statistical investigation is performed. It is found that the contribution of the electric-dipole--electric-quadrupole tensor is often small, except for some special cases that involve C-H stretching vibrations.