Analysis of torsional spectra of molecules with two C3v internal rotors. IV - The torsional potential function for propane-d0 and -d3

The Raman spectra of gaseous propane-d0 and -d3 have been recorded between 50 and 3500 cm. Considerable torsional data are reported and used to characterize the torsional potential function based on a semirigid model. The average 'effective' V3 for the propanes is found to be 1139 plus or minus 10/cm. The sine-sine coupling term is similar in magnitude but opposite in sign to the cosine-cosine coupling term in propane-d0.