Critical evaluation of measured line positions of 14N16O in X2 state

Highlights: • The results of critical evaluation of measured rotation-vibration line positions of ¹⁴N¹⁶O in the X² state are presented. • The analysis was carried out using the fundamental Rydberg-Ritz combination principle, for the available experimental data. • As a result, the precise set of experimental energy levels of NO molecule in the interval 0–35,886 m⁻¹ were obtained. All available line positions for unresolved and resolved Λ-doublets of the ¹⁴N¹⁶O molecule in the X² state were collected from the literature and tested using the RITZ computer code. These data have been critically analysed and used to obtain the most complete set of 1789 experimental energy levels of unresolved Λ-doublets covering the 0–35,866 cm⁻¹ interval. A set of 425 experimental energy levels of resolved Λ-doublets covering the 0–5957 cm⁻¹ interval for two states ²_1/2 and ²_3/2 also have been obtained. These levels together with calculated correlation matrix can be used to generate the precise list of transitions with confidence intervals. Comparisons with the HITRAN as well as with Amiot calculations are discussed. The systematic shift between experimental energy levels of unresolved Λ-doublets and those calculated by Amiot for ²_3/2 state was found. The same systematic shift for transitions frequencies of unresolved Λ-doublets in forbidden subbands ²_1/2↔²_3/2 is also established in the HITRAN database. Comparison of the RITZ energy levels with calculated energy levels by Wong at al. was also done. It was found, that experimental RITZ energy levels for resolved Λ-doublets of ¹⁴N¹⁶O coincide with those calculated by Wong at al. within experimental uncertainties.