Spectroscopy on the first excited torsional state of propylene oxide
The chiral molecule propylene oxide, CH3C2H3O, has been investigated at frequencies between 75–950 GHz using chirped-pulse Fourier-transform emission and conventional absorption spectroscopy. We studied the first excited vibrational mode, ν24, corresponding to the torsional motion of the methyl group. The analysis was done using the internal rotation programs ERHAM and XIAM. Rotational constants and tunnelling parameters were derived, and the A-E splittings due to internal rotation were determined. The potential barrier height to internal rotation, V3, was determined to be V3=898.6611(894) cm-1. Our results are compared with quantum chemical calculations and literature values. The implications of these measurements concerning astrophysical searches of vibrationally excited propylene oxide will be discussed.