Hyper Raman Scattering is a modified Version of Raman scattering, where the scattered Light occurs at frequencies somewhat lower than twice the Frequency of the pump light. This effect is usually rather weak, but has aspects which make it interesting for Raman spectroscopy. In particular, hyper-Raman spectra can provide vibrational information on molecules where ordinary Raman Scattering is suppressed due to symmetry issues (→ silent modes). The effect can be enhanced near optical surfaces.