https://doi.org/10.1351/goldbook.08601
Cubic anharmonic resonance (see anharmonicity), i.e., any interaction caused by cubic terms in the vibrational potential energy.
Notes:
- Traditionally, Fermi resonance was defined as the anharmonic interaction between a fundamental state and one or more overtone or combination transitions.
- Fermi resonance is usually identified by the presence of more than one band of comparable intensity when only one fundamental is expected. Also seen as an Evans hole.