Accurate N2O IR line lists with consistent empirical line positions: ABG-IMRHT and Ames-2000K

Abstract

We report the second generation of Ames N₂O IR line lists, ABG-IMRHT for room-temperature and Ames-2000K for high temperature applications. The ABG-IMRHT line list utilized a new potential energy surface (PES), B1b, refined from a refit of Schröder’s Comp I PES [10.1515/zpch-2015–0622] with σ_rms = 0.006 cm^-1 for all reliable ¹⁴N₂¹⁶O levels in HITRAN2020 [10.1016/j.jqsrt.2021.107949], and a new dipole moment surface (DMS) G10K carrying fitting σ_rms = 6.1 × 10^–7 au up to 10,000 cm^-1. Compared to the previous Ames-296K line list, the PES and DMS upgrades have significantly reduced the line position deviations (δ) and relative intensity deviations (δ %), and maintained consistent accuracy across isotopologues. The line positions of the new ABG (Ames B1b + G10K) line lists including 12 stable N₂O isotopolouges are enhanced by ∼100,000 global EH model based ¹⁴N₂¹⁶O levels from NOSL-296, and empirical levels determined from IAO, MARVEL, RITZ, HITRAN, and JPL(Toth) datasets, hence denoted ABG-IMRHT. Simple 0^th-2^nd order corrections are determined for E_NOSL of about 20 vibrational states above 10,000 cm^-1, based on E_NOSL, E_RITZ, and E_MARVEL comparison. Uncertainty estimates are given for upper and lower state energies (E' and E"), line positions, and IR intensities. The Ames-2000K line list contains 3.4 billion IR transitions covering the 0–15,000 cm^-1 range with J_max=210 and E'/E"=0.125 Hartree (above the PES minimum) for ¹⁴N₂¹⁶O. It combines strengths of three components: “Ames-1″ computed using Ames-1 PES and a weighted DMS “G2d” for 12 isotopologues, “B1b” for ¹⁴N₂¹⁶O computed using B1b PES and G10K DMS with E' < 16,000 cm^-1; and ABG-IMRHT line list. Comparison with HITEMP [10.1016/j.jqsrt.2019.04.040] and UCL TYM (ExoMol) [10.1093/mnras/stae2201] line lists are presented and discussed at T > 1000 K. This study represents a higher level of experiment-model-theory synergy, and a “block” approach for hot IR line list construction. The line lists and related datafiles are available online [10.5281/zenodo.14174306].