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To facilitate the data analysis of current and future high-resolution space telescope missions, we adopt 'Best Theory + Reliable High-resolution Experiment' (BTRHE) strategy to develop highly accurate infrared line lists for nitrous oxide (N2O). The 'Ames-1' potential energy surface (PES) is a CCSD(T)/aug-cc-pVQZ PES refined using selected HITRAN experimental data, with σrms = 0.02–0.03 cm-1 for five isotopologues. The 'Ames-1' dipole moment surface (DMS) is fitted from CCSD(T)/aug-cc-pV(T,Q,5)Z dipoles extrapolated to one electron basis set limit. Using the Ames-1 PES and DMS, Ames-296K line lists are computed in the full range of 0–15,000 cm-1 for 12 N2O isotopologues, with S296K ≥ 10−31 cm-1/molecule.cm-2. The reliability and consistency of Ames-296K intensity predictions (SAmes) are demonstrated through comparisons with HITRAN (SHITRAN), NOSL-296 (SNOSL), recent observed intensities (Sobs) and Effective Dipole Model (EDM) intensities (SEDM). Agreements and discrepancies are discussed, along with preliminary uncertainty estimate for SAmes. The SAmes provides a good constraint to prevent substantial errors in intensity predictions (e.g. for weak bands and minor isotopologues) and can be further improved. Ames-296K and NOSL-296 may complement each other to provide improved input for future database updates, combining the strengths of EH/EDM and BTRHE approaches. Data available at and https://doi.org/10.48667/9kmk-0334. [ABSTRACT FROM AUTHOR]

For line intensity: • Systematic investigation on the isotopologue consistency of CO 2 and SO 2 IR/MW intensity. • Interesting TDM/Einstein-A patterns found for CO 2 vibrational polyads, SO 2 and CO 2 MW, fundamentals, hotbands, etc. For line positions: • First 2nd-round implementation of BTRHE strategy to minimize the isotope/mass dependent residuals. • –– Two orders of magnitude improvement for SO 2 MW prediction accuracy: 0.01-0.02 MHz (A/B/C), 0-5 MHz (J/Ka<20 lines). • This approach starts from and targets at higher accuracy, can easily extend to other bands or molecules. The semi-empirical molecular rovibrational IR line lists, such as ExoMol, TheoReTs, and Ames, combine the experimental accuracy and theoretical power to reach better than 0.1 cm−1 accuracy for line positions and better than 80–90% agreement for line intensities. The quality of these existing semi-empirical IR lists allows further improvements of intensity and line positions for those unobserved minor isotopologues. This paper presents our new BTRHE (Best Theory + Reliable High-resolution Experiment) strategy implementation. For line intensity, the isotopologue consistency and the patterns of mass dependence in the Ames-296 K SO 2 and CO 2 IR lists are quantitatively presented along the mass-inverse coordinates. The consistency and patterns are better than those in existing experimental data. The methodology proposed here can be used to identify inconsistencies, outliers, and mistakes in intensities, and help improve Effective Dipole Model (EDM) and molecular IR databases. We call for an experimental study on the 50006 and 60007 bands of CO 2 628. For line position predictions, a simple approach combining the variational IR line lists with Effective Hamiltonian (EH) model may refine the effective rotational constants A 0 /B 0 /C 0 and quartic centrifugal distortion constants of minor isotopologues. The prediction accuracy may be improved by two orders of magnitude, i.e. reaching 0–5 MHz prediction accuracy in the range of J < 20–30, K a < 10–20, and 0.01–0.02 MHz accuracy for A 0 /B 0 /C 0. Several important factors have been systematically investigated and discussed, e.g. convergence, uncertainties, higher order terms, fixing EH parameters, mass coordinates, etc. A microwave (MW) line set consisting of 644,636 strong transitions (at 296K) for all 30 isotopologues and corresponding refined EH(Ames) parameters are reported in the supplementary material. This approach may be easily extended to rovibrational bands, hot bands, and other molecular systems. [ABSTRACT FROM AUTHOR]

In order to further improve the accuracy of rovibrational IR line lists generated from the "Best Theory + Reliable High-resolution Experiment" (BTRHE) strategy from 0.01 to 0.05 cm−1, or 300–1500 MHz, to ∼10 MHz, we explore the current limits of the Data-Model-Theory synergy by examining the accuracy and consistency of existing data, then propose that "hot" bands in microwave (MW) spectra is the solution we need for future enhancements. The Ames SO 2 J = 0–20 rovibrational energy levels computed on the semi-empirically refined Ames-2 potential energy surface (PES) are fit to the Effective Hamiltonian (EH) model regularly used in the experimental infrared (IR) analysis for SO 2 isotopologues. In the fitted EH(Ames) model, the rotational constants A/B/C and all 5 quartic centrifugal distortion constants display clear, systematic, and consistent patterns along the vibrational state energy or quanta. Such consistent patterns may facilitate the vibrational assignments for MW hot bands and extract more information from high temperature MW spectra. Some EH(Expt) analyses were carried out with the lowest order Coriolis Coupling term, C 1. Their constants should not be directly compared with other EH(Expt) and EH(Ames) results. After excluding them, our δ = EH(Ames)- EH(Expt) analyses for 5 isotopologues (626, 636, 646, 628 and 828) indicates some loss of accuracy and consistency starting from vibrational states as low as 2 ν 2 or 1000 cm−1. Some EH parameters, e.g. δ K , may have relative deviations as large as 50–100% and totally lose any recognizable patterns. This simply means that current EH(Expt) models do not have the system-wide consistency we need to further refine the EH(Ames) and Ames rovibrational IR line lists. A large part of such defects are probably inherited from the limited precision of experimental line positions, i.e. 1E-3 ∼ 1E-4 cm−1, or 3–30 MHz. This is confirmed in a series of truncation tests using the Ames data. Although the EH(Ames) consistency may help identify unreliable rovibrational EH(Expt) parameters, and make reliable predictions for minor isotopologues and unobserved vibrational bands, we believe only the highly accurate "hot" MW transitions can provide real enhancements for EH(Expt) accuracy and consistency. "Hot" MW spectra should play a more significant role in the future synergy of Data, Model, and Theory in the field of rovibrational IR studies. • First systematic and quantitative study to compare the EH(Expt) and EH(BTRHE) models. • Consistency of existing SO2 EH(Expt) models needs improvement to guide the refinement of EH(BTRHE) and line lists. • The 1E-3 ∼ 1E-4 cm-1 data precision of most experimental rovibrational data hurts the EH(Expt) accuracy and consistency. • "Hot" bands in the microwave and Far-IR region are the most promising solution to improve the rovibrational IR analysis. • Including the lowest order Coriolis coupling term affects all EH constants. It makes EH models hard to compare.. [ABSTRACT FROM AUTHOR]