Fourier transform infrared spectroscopy of the ν2 and ν4 bands of NO3

High-resolution Fourier transform infrared spectra of the nu(2) and nu(4) bands of the N-14 and N-15 isotopic species of NO3 were observed in the 762, 742, 365 and 360 cm(-1) regions. Delta K = 3 combination differences of the ground state were obtained by using data of the nu(4) band combined with the nu(3) + nu(4) <- nu(4) band data in the 1127 cm(-1) region and the nu(3) + nu(4) band data in the 1492 cm(-1) region, and the C-0 constant was determined for the first time to be 0.2286274(57) cm(-1) and 0.2286547(58) cm(-1) for (NO3)-N-14 and (NO3)-N-15, respectively. The inertial defects derived from the observed B-0 and C-0 constants were in agreement with the calculated values obtained by using the Coriolis coupling constants zeta(4) = -0.188 for (NO3)-N-14 and -0.156 for (NO3)-N-15 obtained from the analysis of the data. The nu(2) band of (NO3)-N-15 was observed for the first time in the 742 cm(-1) region. In contrast to the case of (NO3)-N-14 reported by Friedl and Sander [J. Phys. Chem. 91 (1987) 2771], the effect of the perturbation from the 2 nu(4) state was found to be small in (NO3)-N-15. However, Coriolis and l-type resonance terms were essential to explain the observed anomalies, such as the staggering in the K' = 3 levels. From an analysis including such interactions, the vibrational energies have been determined for the isomers to be, nu(2) = 762.3405(5), 2 nu(4)(l = 0) = 751.809(18), 2 nu(4)(l = 2) = 771.708(23) cm(-1) for (NO3)-N-14, and nu(2) = 742.7120(3), 2 nu(4)(l = 0) = 742.596(15), 2 nu(4)(l = 2) = 761.219(30) cm(-1) for (NO3)-N-15. Crown Copyright (c) 2012 Published by Elsevier Inc. All rights reserved.