First high-resolution FTIR study of the v1 = v4 = 1 rovibrational state of 14NF3 near 1523 cm−1

The v 1 + v 4 (E, ν0 = 1523.0407 cm−1) perpendicular band of the oblate symmetric top 14NF3 has been studied by FTIR spectroscopy with a resolution of 2.5 × 10−3 cm−1. In total, 1885 rovibrational transitions up to K max = 70 = J max have been assigned. Due to the k(Δl = 0, Δk = ±6) interaction (h 3 = 2.22 × 10−13 cm−1) within the kl = +4 sublevel, large A+/A− doublets were identified from J = 24 to J = 33 and large A +/A − doublets due to l(Δl = ±2, Δk = ±2) rotational resonance (q 4 = 1.730 × 10−3 cm−1) within the kl = +1 level were also observed, while the effect of the expected l(Δl = ±2, Δk = ∓ 4) interaction was not detected on the ΔK = −1 transitions owing to their vanishing intensity. The same D-reduction Hamiltonian model taking into account intravibrational resonances, recently performed for the v4 = 1 (E, ν0 = 493.4227 cm−1) state of 14NF3, was employed. Assuming the v1 = v4 = 1 vibrational state as isolated, the nonzero weighted experimental data were fitted to 26 free parameters with a standa...