The Rotational/Concerted Torsional Spectrum of the g′Ga Conformer of Ethylene Glycol

✍ Scribed by D. Christen; L.H. Coudert; R.D. Suenram; F.J. Lovas

• Publisher: Elsevier Science
• Year: 1995
• Tongue: English
• Weight: 936 KB
• Volume: 172
• Category: Article
• ISSN: 0022-2852
• DOI: 10.1006/jmsp.1995.1155

✦ Synopsis

The microwave spectrum of the (g^{\prime} G a) conformer of ethylene glycol has been assigned for the first time using microwave-microwave double resonance and molecular beam Fourier transform microwave spectroscopy. Such techniques were necessary in order to select the desired lines in the crowded spectrum, which does not follow a rigid rotator pattern because of the large-amplitude motion displayed by the molecule. This motion, consisting of a concerted torsion of both (\mathrm{OH}) groups, leads to a tunneling splitting of (7 \mathrm{GHz}) and significantly alters the rotational energy level pattern because it is coupled to the overall rotation of the molecule through a Coriolis coupling. This coupling is accounted for using an IAM-like theoretical model, and this allows us to satisfactorily analyze the microwave frequencies of the normal and of the (\mathrm{O}-d_{2}) species. Information on the equilibrium geometry of the molecule and on the tunneling path is extracted through the values obtained for the parameters involved in this Coriolis coupling. A dipole moment analysis yields values of all three dipole moments components and a determination of their relative signs is attempted. 1995 Academic Press, Inc.