Microwave rotational spectral study of CH3CN-H2O and Ar-CH3CN

The microwave spectrum of the molecular complex of acetonitrile (CH3CN) with water (H2O) has been studied with a pulsed-beam Fourier Transform Microwave Spectrometer (FTMW) from a gas sample of 1% by volume of CH3CN in Ar flowed over a water sample. The frequency coverage was about 922 GHz for various isotopomers. The CH3CN-H2O complex exhibited a symmetric top spectrum for two tunneling components, whereby the water subunit tunnels between two equivalent forms. The molecular structure was determined with the aid of spectral studies of isotopically substituted monomers containing C-13, N-15 and O-18 and mono- and di-deuterated water. In the process of measuring the (CH3CN)-C-13-H2O species, we observed some nearby transitions for the Ar-(CH3CN)-C-13 complex. Since the molecular structure of the Ar complex in the literature was not completely determined, we also measured several isotopomers of it to improve the molecular structure. The rotational analyses provide the rotational, centrifugal distortion and nuclear quadrupole coupling constants for all of the isotopomers analyzed. Published by Elsevier Inc.