INTENSITIES OF CH-STRETCHING OVERTONES IN 2-BUTENES

The gas phase vibrational overtone spectra of trans-2-butene and cis-2 -butene are recorded in the Delta v(CH) = 1-6 regions by Fourier trans form infrared and conventional near infrared-visible spectroscopy. Ove rtone spectra in the Delta v(CH) = 5-9 regions are recorded by intraca vity dye/titanium: sapphire laser photoacoustic spectroscopy. Absolute oscillator strengths are obtained from the conventional spectra. Osci llator strengths are calculated with a harmonically coupled anharmonic oscillator local mode model and ab initio dipole moment functions. Th e experimental and calculated oscillator strengths are compared. Spect ral absorptions that are not due to transitions to pure local mode sta tes or to local mode combination states, are observed in the spectra o f both molecules, and are believed to be due to absorptions that invol ve methyl group torsion.