When light scattered by a molecule and the freency of the scattered light is changed, this phenomenon is called

The phenomenon where light is scattered by a molecule and the frequency of the scattered light changes is known as the Raman effect [1]. This is a form of inelastic scattering where energy is exchanged between the incident photons and the vibrational or rotational states of the molecule [2]. In contrast, Rayleigh scattering is an elastic process where the frequency of the scattered light remains unchanged. The Raman effect results in scattered photons having lower energy (Stokes shift) or higher energy (anti-Stokes shift) compared to the incident light [2]. This frequency shift provides a unique 'fingerprint' of the molecular vibrations, which is the fundamental principle behind Raman spectroscopy [2]. Other options like the photoelectric effect involve electron emission, and Rutherford scattering involves alpha particles, neither of which describe molecular light scattering with frequency changes.

Sources

1. [1] https://www.chm.bris.ac.uk/pt/diamond/jakethesis/jake-thesis.pdf
2. [2] https://pmc.ncbi.nlm.nih.gov/articles/PMC6626094/