A COMPLEX OF MOLECULAR FLUORINE WITH AN ORGANIC-COMPOUND DETECTED IN THE GAS-PHASE - THE ROTATIONAL SPECTRUM OF CH3CN-CENTER-DOT-CENTER-DOT-CENTER-DOT-F-2

A complex of methyl cyanide and molecular fluorine was detected by usi ng a fast-mixing nozzle in a Fourier-transform microwave spectrometer. Ground-state rotational spectra of three symmetric-top isotopomers (C H3CN)-N-14 ... F-2, (CD3CN)-N-14 ... F-2 and (CH3CN)-N-15 ... F-2 were analysed to give the spectroscopic constants B-0 D-J D-JK, H-JK and c hi(aa)(N-14) Interpretation of the spectroscopic constants revealed th at the order of the nuclei on the molecular symmetry axis is C-C=N ... F-F, that r(N ... F-i) = 2.748(3) Angstrom and that the complex is we akly bound as judged by the value of the intermolecular stretching for ce constant k(sigma) = 2.5 N m(-1) and the bending force constant k(th eta) = 4 X 10(-21) J rad(-2).