FERMI RESONANCE NONLINEAR WAVES AND SOLITONS IN ORGANIC SUPERLATTICES

摘要

Fermi resonance is a phenomenon which takes place in vibrational or electronic spectra of molecules. For example, let a molecule have two vibrational modes with frequencies ω_a and ω_b. If the second order resonance condition 2ω_a (≌) ω_b is fulfilled, then the hω_b transition in infrared spectrum can be split into two lines of comparable intensity and the second line cannot be explained as a result of interaction of light with the vibrational a mode because the transitions with excitation of two hω_a quanta are forbidden due to well-known n → n ± 1 selection rule for harmonic oscillator. E. Fermi explained this experimental observation as a result of nonlinear resonance interaction of two vibrational modes with each other.