original_query: What is the similarity between illouin spectroscopy and Raman spectroscopy?
  What is the most relevant chunk to answer the query?
query: What is the similarity between Brillouin spectroscopy and Raman spectroscopy?
answer: Both Brillouin and Raman spectroscopy involve similar physical scattering processes, but the information gained is different. Raman spectroscopy focuses on high-frequency molecular vibrational modes, while Brillouin spectroscopy focuses on low-frequency phonons related to elastic properties.