Fermi resonance

{
  "id": "MLC-T-CHM-004381",
  "term": "Fermi resonance",
  "field": "Chemistry",
  "definition": "A spectroscopic phenomenon where two vibrational energy levels of similar energy and symmetry interact, leading to a shift in their observed frequencies and an increase in the intensity of the weaker band. This interaction occurs when a fundamental vibration has nearly the same energy as an overtone or combination band. It results in characteristic splitting patterns in infrared and Raman spectra.",
  "subject": "Analytical Chemistry",
  "see_also": [
    "Evans hole",
    "mechanical anharmonicity",
    "combination transition",
    "vibrational potential energy"
  ],
  "references": [
    "PAC, 2021, 93, 647. 'Glossary of methods and terms used in analytical spectroscopy (IUPAC Recommendations 2019)' on page 746 (https://doi.org/10.1515/pac-2019-0203)"
  ],
  "url": "https://mlchart.com/terminology/chemistry/fermi-resonance/"
}