CONFORMATIONAL DEPENDENCE OF INTRAMOLECULAR VIBRATIONAL-ENERGY REDISTRIBUTION IN THE ETHYLENIC=CH2 STRETCH FUNDAMENTAL OF ALLYL FLUORIDE

The high-resolution (6 MHz) infrared spectra of the asymmetric ethylen ic hydride stretches of both cis and gauche allyl fluoride have been m easured. Rotational assignments of the eigenstates are made using the groundstate microwave-infrared double-resonance capabilities of an ele ctric resonance optothermal spectrometer (EROS). The cis vibrational b and near 3114 cm(-1) is characterized by sparse, narrow IVR multiplets resulting from weak Coriolis or cross conformer interactions between the vibrational bath states. The IVR lifetime of the cis vibrational b and is approximately 2 ns (2000 ps). The gauche vibrational band near 3100 cm(-1) is qualitatively and quantitatively quite different from t he cis band. The gauche band is characterized by significantly fragmen ted NR multiplets with an average IVR lifetime of about 90 ps. The mea sured anharmonic state density of the gauche band is about 30 states/c m(-1). The disagreement between the measured state densities of the ga uche vibrational band and the calculated values suggest that the gauch e vibrational states do not interact with cis vibrational states. For two IVR multiplets of the gauche band, the transitions were assigned a ccording to the parity of the rovibrational bright state. The two pari ty states show roughly the same dynamical behavior. Also, RRKM calcula tions of the unimolecular isomerization rate are performed and compare d to experimental results. The RRKM calculations overestimate both the cis and gauche isomerization rates by orders of magnitude.