Coherent spectroscopy of Mandelstam-Brillouin scattering in spatially inhomogeneous media

Mandelstam-Brillouin (MB) steady-state scattering in an elastic medium with a dense local zone inhomogeneity is considered in the 1D approximation. It is shown that for a certain size of inhomogeneity, the scattered radiation spectrum contains individual resonances whose frequencies depend on the elastic properties of microscopic inclusions. Experiments were performed using coherent four-photon scattering spectroscopy in the range 0–1 cm⁻¹ with a resolution of 0.06 cm⁻¹ in specially processed distilled water and in an aqueous solution of α-chymotrypsin albumin. In both media, the presence of MB resonances displaced is detected relative to the water resonance (≈0.25 cm⁻¹) in different directions and corresponding to different types of microinclusions.