Figure 1.

Schematic of Raman scattering. (a) Raman scattering is classified into Stokes and anti-Stokes Raman scattering based on the vibrational energy changes. Relative to the incident energy, vibrational energy of the scattered light is lower in the case of Stokes Raman scattering, higher in the case of anti-Stokes Raman scattering, and constant for Rayleigh scattering. (b) The scattering of photons by irradiated molecules is predominantly elastic (Rayleigh scattering), accounting for approximately 99.9% of the scattered light. The remaining 0.1% of the scattering is attributed to an inelastic Raman scattering.