Observation of Tunneling States within the Two Conformations of Hydroxyl gauche, Methyl Asymmetric CH2DCH2OH.

Fourier transform microwave (FTMW) spectroscopy has been used to observe and resolve the 60-kHz tunneling splitting between the symmetric and antisymmetric substates of conformations I and II for hydroxyl gauche, methyl asymmetric CH2DCH2OH. Conformation I has the hydroxyl H and methyl D on the same side of the molecular plane whereas conformation II has them on the opposite sides. The determination of the small energy difference between these two conformers leads to an improved value of Vs1s2, (the potential energy coefficient that localizes the molecule into conformations I and II) of 4.8(5) cm-1. Further, the relative intensities of the spectra show that conformation II is lower in energy than conformation I. Analysis of the quadrupole splittings of the a-type 101-000 transitions determines values for eQqaa that range from -87 to -98 kHz for both hydroxyl conformations with the methyl group asymmetric and +84 to +102 kHz for both hydroxyl conformations with the methyl group symmetric. Copyright 1998 Academic Press.