Changes of vibrational lifetimes with minor structural modification of small polyatomic molecules

Substantial changes of population lifetimes of CH-stretching modes
are observed when two atoms are exchanged in CH2=CCl2 to form trans
CHCl=CHCl and when three deuterons are substituted in C6H6 to form
1,3,5.-C6H3D3. The measured lifetimes are in good agreement with
estimates based on Fermi resonance-mixing which is inferred from
infrared and Raman spectra.