MICROWAVE SPECTRUM AND STRUCTURE OF THE METHANOL-WATER COMPLEX

Abstract

The a-type spectrum of the methanol-water complex was observed in a pulsed beam Fourier transform microwave spectrometer for $J=0\rightarrow 1$ and $J=1 \rightarrow 2$ and in a cw slit-jet direct absorption spectrometer for $J=2 \rightarrow 3$ to $J=6-7$. Analysis of the assigned lines possessing a second order Stark-effect (i.e. $m=0$ for the methyl rotor) yields the rotational constants for the normal isotopic species: $A=28332 MHz. B=4232.07 MHz, C=3746.72 MHz$. Stark-effect measurements on the normal isotopic species were analyzed to give dipole moment components of $\mu_{a} = 2.385(8) D. \mu_{b} = 1.090(6) D, \mu_{c} = 0.13(14) D$. Preliminary structural analysis using the above rotational constants shows that the complex is hydrogen-bonded with the methanol subunit acting as the hydrogen bond acceptor and with a geometry similar to that for the water dimer. There is no indication thus far of a water acceptor complex. Further work is in progress on the $^{13}C$ isotopomer as well as various D substituted isotopomers. and a more detailed spectral and structural analysis will be presented. In addition, splittings of observed transitions will be discussed with respect to the recent group theoretical analysis of Hougen and Ohashi [1].