Anti-Stokes Scattering

Anti-Stokes scattering occurs when light interacts with a material and gains energy from it, causing the scattered light to have a higher frequency (or shorter wavelength) than the original. This happens when the material's molecules are already excited (due to heat), and when hit by photons, they transfer some of their internal energy to the light. Consequently, the scattered light becomes slightly more energetic. This effect is useful in techniques like Raman spectroscopy for temperature measurement and studying molecular interactions, as it provides information about the vibrational state of molecules within the material.