Analysis of 14N18O Spectrum in the 5200–5500 сm−1 Spectral Region

The absorption spectrum of ¹⁴N¹⁸O molecule in the 5200–5500 сm⁻¹ region was recorded for the first time using a Bruker IFS 125M Fourier spectrometer with a spectral resolution of 0.0056 сm⁻¹. The analysis of the spectrum made it possible to detect the vibrational–rotational lines of the 3–0 band of the main transitions in the X²Π electronic state of the ¹⁴N¹⁸O molecule. For the main ²Π_1/2–²Π_1/2 and ²Π_3/2–²Π_3/2 transitions, positions of 102 lines from a Λ-doublet were recorded in three branches. The positions and relative intensities of each component of the doublet were determined for 61 resolved doublets. The maximal rotational quantum number J was 29.5. The experimental line positions in the 3–0 band confirm the calculated data presented in HITRAN database. The frequencies of recorded transitions, weighted in accordance with experimental uncertainties, were processed, and the spectroscopic constants were determined for the vibrational state \({v}\) = 3. With the found spectroscopic constants, we predicted the rotational energy values up to J = 35.5 for the vibrational state \({v}\) = 3 and transition frequencies in the 3–3 and 3–0 vibrational bands for the ²Π_1/2 and ²Π_3/2 electronic states. The calculation results agree with the data given in HITRAN within the error specified in this database.