Spectroscopy of C-H stretching vibrations of gas-phase cyclohexene

The fundamental and overtone spectra of the C-H stretching of cyclohexene i n the gas phase have been measured using FTIR spectroscopy in the range 280 0-11 500 cm(-1) (Delta v = 1-4) and intracavity dye laser spectrometry in t he range 12 900-17 500 cm(-1) (Delta v = 4-7). Up to Delta v = 6, the spect ra show disturbed structure. The transitions observed are mainly interprete d on the basis of a comparative study with the previous experimental and th eoretical work relative to 3,3,6,6-d(4)-cyclohexene. Ab initio calculations of molecular geometries and fundamental vibrational frequencies have also been performed in a molecule-fixed cartesian coordinates to calculate the f irst derivative of the dipole moment function and of the polarisability ten sor in order to reproduce the fundamental infrared and Raman spectra, In th e overtone spectra, possibility of Fermi resonances between the methylenic C-H bond stretchings and combination states involving other low-frequency m odes is qualitatively discussed. (C) 2000 Elsevier Science B.V. All rights reserved.