Re-analysis of ammonia spectra: Updating the HITRAN 14NH3 database

The data incorporated in the HITRAN database for 14NH3 are analyzed using a comprehensive and consistent set of quantum numbers, empirical lower energy levels and the BYTe variationally calculated line list as reference points. Labelings are checked to ensure that they obey both the usual selection rules and the HITRAN labeling formalisms; the problems identified are corrected where possible. Further assignments are brought into question by combination difference (CD) checking of implied upper energy levels. The CD analysis yields an 89% complete 14NH3 energy level list up to 6610 cm−1 and J=21, self-consistent to 0.1 cm−1. In combination with the 1723 previously unassigned and unlabeled lines in HITRAN a total of 2529 problem lines were identified for re-analysis. The compiled energy level list was used to label and assign the set of problem transitions, resulting in a total of 249 new assignments and a further 368 new labelings. Assignment by comparison with the reference line list resulted in 111 further new line assignments and 14 new labelings. Intensities are checked against recent measurements and BYTe. New intensities are proposed for the ν2 band with new intensities and line positions for the 2ν2−ν2 and new line lists are created for the ν2−ν2, ν2−ν4 and ν4−ν4 bands. BYTe band intensities are analyzed to identify other regions of missing intensity.

•The ammonia lines in the HITRAN database thoroughly reanalysed.•Line assignments corrected and new assignments made.•Issues with the line intensities for the nu2 band identified and corrected.•Lines for four bands from measured energy levels and ab initio intensities.