Experimental values of the rotational and vibrational constants and equilibrium structure of nitrogen trifluoride

Abstract Several accurate experimental values of the rovibrational interaction constants α C and α B , the harmonic wave-number parameters ω ij , and the anharmonicity x ij and g ij constants have been extracted from the most recent high-resolution Fourier transform infrared (FTIR), centimeter-wave (CMW) and millimeter-wave (MMW) measurements in the spectra of the oblate symmetric top molecule 14 NF 3 . The data used are those of the four fundamental, the overtone, the combination and the hot bands identified and analyzed in the range between 400 cm −1 and 2000 cm −1 . Combining the recent experimental values of the constants α C and α B , with the accurate experimental ground state rotational constants C 0 and B 0 , new equilibrium rotational constants have been evaluated: C e  = 0.1968006 (26) cm −1 and B e  = 0.358981442 (43) cm −1 for the pyramidal molecule NF 3 , from which the following equilibrium structure is obtained: r e (F-N) = 1.36757 (58) A; θ e (FNF) = 101.8513 (10)°. This experimental equilibrium geometry is in excellent agreement with the recent structure determined by ab initio calculations at the CCSD(T)/aug-cc-pVQZ level of theory.