Rotational spectrum and properties of a gas-phase complex of molecular fluorine and hydrogen cyanide

Ground-state rotational spectra of three isotopomers (HCN)-N-14 ... F-2, (HCN)-N-15 ... F-2 and (DCN)-N-14 ... F-2 of a complex formed by hydrogen cyanide and molecular fluorine were observed by using a fast-mixing nozzle in a Fourier transform microwave spectrometer, Effects of F-F spin-spin and F-spin rotation coupling were observed in the spectra of (HCN)-N-15 ... F-2 and (HCN)-N-14 ... F-2 and allowed for in the analysis. Spectroscopic constants B-O, D-J and X(aa)(N-14) appropriate to a linear molecule HCN ... F-2 were determined and interpreted in terms of the geometry and binding strength of the complex, Properties of several axially symmetric complexes involving the N ... X(2) weak bond (X=F or Cl) are compared.