Improved potential energy surface and spectral assignments for ammonia in the near-infrared region

A new ‘spectroscopic’ potential energy surface (PES) for14NH3has been generated by refinement of a high accuracy ab initio PES to experimental data. The quality of the PES is reflected in the excellent agreement between calculated rovibrational energy levels and the empirical values of MARVEL. The PES is used in conjunction with two different DMSs to generate room temperature line lists up to 12 000 and 20 000 cm−1, including all transitions from lower states up to 4000 cm−1, with total angular momentum up to J=20. Several strong bands are found to be missing from HITRAN 2016 in the 5700–6200 cm−1 region. Using the line lists, 769 transitions in the 7400–8000 cm−1 are assigned by ground state combination difference (GSCDs), along with empirical upper state energies and full quantum labels for 284 levels. 53 of our assignments were found to disagree with those given in HITRAN 2016