Analysis of torsional spectra of molecules with two internal C3v rotors. IX - The torsional potential functions of isobutene-d0 and -d6

Raman spectra of gaseous isobutene (CH3)2C=CH2 and isobutene-d6 have been recorded between 100 and 500/cm with a resolution of 1/cm, and the far-IR spectra of the same compounds have been recorded over the same frequency range with a resolution of 0.5/cm. Several torsional transitions have been observed for both molecules and these data have been used to determine the torsional potential function based on a semirigid model. Values of average effective barrier were determined for the molecules.