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

Ground-state rotational spectra of three isotopomers HC14N … F2, HC15N … F2 and DC14N … F2 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 HC15N … F2 and HC14N … F2 and allowed for in the analysis. Spectroscopic constants B0, DJ and ξaa(14N) appropriate to a linear molecule HCN … F2 were determined and interpreted in terms of the geometry and binding strength of the complex. Properties of several axially symmetric complexe involving the N … X2 weak bond (X = F or Cl) are compared.