Infrared spectroscopy of 14 ND 3 : Analysis of the ν 2 /ν 4 /2ν 2 and ν 1 /ν 3 /2ν 4 band systems

The high resolution infrared spectrum of 14ND3 has been re-investigated in the intervals 450 - 1600 cm-1 and 2200 - 2800 cm-1, where the absorption lines of the nu2/nu4/2nu2 and nu1/nu3/2nu4 band systems are located. The analysis of the bending fundamentals nu2 and nu4 has been extended assigning 844 transitions belonging to the 2nu2 and 2nu2 - nu2 cold and hot bands. In total, 3436 transitions, of which 3358 are vibration-rotation-inversion and 78 inversion transitions in the v2 = 1 state [Urban Š et al. J Mol Spectrosc 1984;106:29-37] have been fitted simultaneously. The effective Hamiltonian adopted for the analysis includes all symmetry allowed interactions between and within the studied excited state levels. Accurate values of the spectroscopic parameters for both inversion components of the v2 = 1, 2 and v4 = 1 states have been obtained. The inversion transitions are reproduced at 1.8 times their experimental estimated precision, while the infrared data are reproduced at 1.5 times their uncertainties. The assignments of the stretching fundamentals nu1 and nu3 have been extended to higher J and K transitions. The number of transitions of nu1 has been doubled and it has been increased by 23% for nu3. In addition, 805 transitions reaching the v4 = 20 and 2+2 s, a states have been identified. In total, 2408 transitions of the nu1/nu3/2nu4 band system have been fitted simultaneously. The adopted effective Hamiltonian includes also the Fermi resonance terms between v1 = 1 and v4 = 20 and higher order Coriolis terms between v1 = 1/v4 = 2+2, v3 = 1/v4 = 20, and v3 = 1/v4 = 2+2. The model adopted to rationalize the entangled network of energy levels has been moderately successful. The standard deviation of the fit, 0.0090 cm-1, is 9 times the estimated measurement precision. Finally, an improved set of ground state parameters has been derived.