Pulsed Molecular Beam Microwave Fourier Transform Spectroscopy of the van der Waals Trimer Ar2-CO2

✍ Scribed by Y.J. Xu; W. Jager; M.C.L. Gerry

• Publisher: Elsevier Science
• Year: 1993
• Tongue: English
• Weight: 414 KB
• Volume: 157
• Category: Article
• ISSN: 0022-2852
• DOI: 10.1006/jmsp.1993.1011

✦ Synopsis

The microwave rotational spectrum of the van der Waals trimer (\mathrm{Ar}{2}-\mathrm{CO}{2}) has been observed between 7 and (18 \mathrm{GHz}) using a Balle-Flygare type pulsed molecular beam microwave Fourier transform (MWFT) spectrometer. Twenty-one transitions, all (b)-type, (K_{a}+K_{c}=) even, have been assigned. The rotational constants and centrifugal distortion constants have been determined. The trimer has been found to be a (C_{2 v}) distorted tetrahedral shaped highly asymmetric top ( (\kappa=) (\sim 0.360) ). The effective Ar-Ar distance and the two Ar-C distances have been evaluated and have been found to be similar to the corresponding values reported for the (\mathrm{Ar}{2}) dimer and for (\mathrm{Ar}-\mathrm{CO}{2}), indicating that pairwise additivity is the dominating influence in the trimer bondings. A harmonic force field analysis has been performed on the basis of the centrifugal distortion constants. The estimated Ar-Ar stretch frequency of (\mathrm{Ar}{2}-\mathrm{CO}{2}) is (23.5 \mathrm{~cm}^{-1}), which compares favorably with 25.7 (\mathrm{cm}^{-1}) reported for the (\mathrm{Ar}{2}) dimer. A comparison of the structures and the van der Waals force constants of (\mathrm{Ar}{2}-\mathrm{CO}{2}) with other reported (\mathrm{Ar}{2})-small molecule trimers is given. 1993 Academic Press. Inc.