THE MILLIMETER-WAVE SPECTRA OF FN2+ AND FCO+ AND ABINITIO CALCULATIONS FOR FCN, FCO+, FN2+ AND FNC

The millimeter-wave spectra of FN2+ and FCO+ were obtained in a liquid-nitrogen-cooled discharge of a mixture of F2 and N2 or CO. Fifteen and thirteen lines were measured for FN2+ and FCO+, respectively, from the positions of which rotational constants of 11 154.83371(70) and 10 768.6958(11) MHz were derived. Accompanying ab initio calculations predict ground state dipole moments of 0.556 and -0.269 D for the two cations. An unusually large wavenumber of 2456 cm-1 is obtained for ν3, the pseudoasymmetric stretching vibration of FCO+. The ground state rotational constant and the electric dipole moment of isoelectronic FNC, which is less stable than FCN by 285 kJ mol-1, are predicted to be 10 881(50) MHz and -1.583(30) D, respectively. © 1992.