CH STRETCHING OVERTONE SPECTRA OF TRIMETHYLENE OXIDE AND TRIMETHYLENESULFIDE

The room temperature vapor phase CH stretching overtone spectra of tri methylene oxide and trimethylene sulfide are recorded in the Delta ups ilon(CH) = 2-7 regions. The spectra are interpreted with the local mod e model and are assigned in part on the basis of ab initio calculated CH bond lengths. Ab initio geometry optimizations are carried out at t he MP2 level with three different basis sets [6-31G(d), 6-311+G(d,p), and 6-311++G(2d,2p)] for both molecules and with a QCISD/6-31G(d) calc ulation for trimethylene oxide. Spectral structure not due to pure loc al mode transitions of to local mode combinations is tentatively assig ned to transitions to states that involve the interaction of CH stretc hing and ring puckering motion.