Knowledge Bank

The microwave spectrum of the $g-1Ga$ conformer of ethylene glycol has finally been assigned using a microwave-microwave double resonance (MWMWDR) spectrometer. Some lines were also measured using a molecular beam Fourier Transform microwave (MB-FTMW) spectrometer. These selective techniques were paramount to assign single transitions in a very crowded spectrum that, due to a large amplitude concerted torsion of the hydroxy1 groups, does not follow a rigid rotor pattern. The tunneling torsion (splitting 7 GHz) couples to the overall rotation of the molecule through coriolis coupling. This coupling is accounted for using an I AM - like theoretical model. Information on the equilibrium geometry of the molecule and its tunneling path is extracted through the values obtained for the parameters involved in the Coriolis coupling and compared with ab initio calculations.