MICROWAVE-SPECTRUM, DIPOLE-MOMENT, AND DYNAMIC STRUCTURE OF THE LINEAR HCCH-CO DIMER

Rotational spectra have been observed for several C-13/O-18 isotopic species of the pseudolinear acetylene-carbon monoxide dimer using the pulsed, Fourier transform Balle/Flygare microwave spectrometer. A quadrature detection system has been incorporated in the data processing system to avoid folding of the spectrum onto itself in taking the Fourier transform. Dipole moments of 0.3112(12) and 3.29(3) D were determined for the parent HCCH-CO species and for HCN-HCCH, respectively. Structural properties were derived from the various measurements, including a well depth of 300 cm-1 from D(J), and the results are compared with those reported earlier for HCN-HCCH. A substitution analysis is developed in which the rotational properties of a pseudolinear dimer are treated as a symmetric top. A simple method is described for determining effects of the off-axis bending of the monomers.