[′mäj·ə‚lād·əd ′rä·mən ‚skad·ə·riŋ] (spectroscopy) Application of modulation spectroscopy to the study of Raman scattering; in particular, use of external perturbations to lower the symmetry of certain crystals and permit symmetry-forbidden modes, and the use of wavelength modulation to analyze second-order Raman spectra.