Raman spectroscopy in which scattering occurs through hyperpolarizabilities. A two-photon technique in which an intense pulsed beam of electromagnetic radiation is focused onto the sample. When sufficient power is present in the pulse, two photons may interact with the one molecule to create a virtual state at double the frequency of the laser excitation. Raman scattering from this virtual state to an excited vibrational state of the ground state then occurs.