High-Resolution Infrared Spectroscopy of the v1 + v4 Band of 14NF3: Reductions of the Rovibrational Hamiltonian

The high-resolution Fourier transform infrared spectrum of nitrogen trifluoride NF3 has been studied in the v(1) + v(4) perpendicular band region around 1523 cm(-1). All experimental data have been refined applying various reduction forms of the effective rovibrational Hamiltonian developed for an isolated degenerate state of a symmetric top molecule. The v(1) = v(4) = 1 excited state of the (NF3)-N-14 oblate molecule was treated with models taking into account l- and k-type intravibrational resonances. Parameters up to sixth order have been accurately determined and the unitary equivalence of the derived parameter sets in different reductions was demonstrated.