Analyses of the Infrared Absorption Bands of 15NO3 in the 1850-3150 cm-1 Region

We have observed the infrared spectrum of (NO3)-N-15 by a high resolution Fourier transform infrared (FT-IR) spectrometer using the reaction of F atoms with (HNO3)-N-15. Five E-2'-(2)A(2)' bands ire identified in the 1850-3150 cm(-1) region. The rotational analyses indicate that these bands have the lower state in common, which coincides with the ground state of planar D-3h symmetry. The upper E-2' states more or less suffer from perturbations by close-lying dark states. Among them, those of the 2004, 2128, and 2492 cm(-1) bands are analyzed to determine molecular parameters in these states by fixing the ground-state constants to those derived by a combination difference method. The spin-orbit and Coriolis coupling constants in the E-2' states are substantially different for different vibronic states, The vibrational assignments of NO3 in the ground electronic state are discussed using experimental data heretofore available, Supplemented by those obtained by the present study.