The harmonic force field and rz structure of HNCO

The presently available microwave, millimeter wave, and far-infrared data of five isotopic species of isocyanic acid, namely, HNCO, H15NCO, HN13CO, HNC18O, and DNCO, have been used to obtain improved values of the ground-state rotational constants, the five quartic distortion constants, and some higher-order distortion constants in the Ir S reduced Hamiltonian of Watson. The appropriate planarity relation among the quartic centrifugal distortion constants has been imposed in the fitting procedure. The general harmonic force field of isocyanic acid has been determined using all existing data, and assuming a trans bent equilibrium geometry of the molecule with an NCO angle of 170°. Finally an rz structure has been obtained using the Az, Bz, and Cz rotational constants of five isotopic species. The bending of the NCO chain is found to be 8° in the trans configuration

The \u3bd 1 and \u3bd 3 band system of 15NH3

The infrared spectrum of 15NH3 has been investigated by high-resolution Fourier transform infrared spectroscopy in the region of the stretching fundamentals. A large number of ro-vibration transitions in the 3050\u20133650 cm1 spectral range has been recorded and assigned to the fundamentals 1 and 3, and to the 24 overtone bands. In total, 1606 transitions involving the (s) and (a) inversion\u2013rotation\u2013vibration levels have been identified and assigned. They include 256 perturbation-allowed transitions with selection rules DK\ubc2, Dl\ubc1 in 3 and Dl\ubc\ufe2 in 22 4 , and DK\ubc3, Dl\ubc0 in 1 and 204 . All assigned transitions were fitted simultaneously to a model Hamiltonian that includes all symmetry-allowed interactions between and within the excited state levels in order to obtain accurate sets of spectroscopic parameters for both inversion states. The standard deviation of the fit, 0.034 cm1, is about 70 times larger than the estimated measurement precision. This result is similar to that reported for the same band system in 14NH3 by Kleiner et al. [J. Mol. Spectrosc. 193, 46 (1999)] and is a consequence of the neglect of vibration and ro-vibration interactions between the analysed states and vibrationally excited states with close energies

The infrared spectrum of 13C2HD between 100 and 2100 cm-1: a global fit of the bending states up to v4+v5 =3.

International audienceThe fundamental bending ro-vibrational bands and a number of overtone, combination and hot bands of 13C2HD have been recorded by Fourier transform infrared spectroscopy (FTIR) in the range 450-2100 cm-1. In addition, the v5-v4 band, centred at 164.65 cm-1, has been identified in a spectrum of 13C2H2. The data have been analysed simultaneously in a global fit that has provided very accurate rotational and vibrational parameters for the ground and for the vibrationally excited states

Perturbation allowed transitions in the infrared spectrum of 14ND3: determination of the K-dependent parameters in the ground state

Accurate values of the K-dependent constants (i )C, (i )DK and (i )HK in the ground state of 14ND3, with i = s, a, have been determined for the first time thanks to the detections of \u2018perturbation allowed\u2019 transitions in the \u3bd1, \u3bd2, \u3bd3, \u3bd4 and 2\u3bd4 infrared bands. The rotation\u2013inversion and inversion transitions from the literature, together with 7289 ground state combination differences from the infrared vibration\u2013rotation\u2013inversion transitions have been simultaneously analysed. The adopted rotation\u2013 inversion Hamiltonian includes distortion constants up to the eighth power and thek=\ub13 andk =\ub16 interaction terms. Precise values of the diagonal constants and of thek=\ub13 interaction coefficients have been obtained. Accurate values of the ground state term values have been calculated for both s and a levels up to J = 21

The infrared spectrum of (13)C2H2 in the 60-2600 cm-1 region: bending states up to v4+v5=4

info:eu-repo/semantics/publishe