Fermi resonance

Fermi resonance occurs when two vibrational energy levels in a molecule are very close together, causing them to interact and exchange energy. This interaction shifts their energies and alters their spectral signals, making them appear at different frequencies than expected. It's like two musical notes that are nearly the same pitch blending and affecting each other's sound. This phenomenon helps scientists understand complex molecular behaviors and the environment within molecules, especially in infrared spectroscopy, by revealing subtle interactions between vibrational modes that are otherwise difficult to detect.