Spectroscopic characterization of the v2 = 3 and v2 = v4 = 1 states for 15NH3 from high resolution infrared spectra

The a, s inversion levels of v2 = 3 and v2 = v4 = 1 vibration states of 15NH3 are studied from high resolution infrared spectra up to 3200 cm−1. Spectra were recorded from 60 to 2000 cm−1 using the Bruker IFS 125 interferometer located at the Canadian Light Source and from 1900 to 3200 cm−1 using the Bomem DA 008 in Bologna. Transitions in 3ν2 and ν2+ν4, in the 3ν2 ← ν2, ν2+ν4 ← ν2, 3ν2 ← 2ν2, ν2+ν4 ← 2ν2, 3ν2 ← ν4, ν2+ν4 ← ν4, and 3ν2 ↔ ν2+ν4 hot bands, and the rotation-inversion transitions in 3ν2 and ν2+ν4 have been observed. 5770 transitions with J max ′ / K max ′ up to 15 have been assigned, including 395 perturbation allowed ones. All transitions were fitted simultaneously on the basis of a rotation-inversion Hamiltonian which includes distortion constants up to 10th power in the angular momentum and all symmetry allowed interaction parameters between and within the a, s inversion levels of v2 = 3 and v2 = v4 = 1. The term values of the lower levels of transitions have been calculated using the parameters recently derived for the ground and v2 = 1, 2 and v4 = 1 states. The data were reproduced at experimental accuracy. The results are compared with those of 14NH3. The experimental transitions are compared with their theoretically predicted values. The list of assignments is supplied as supplementary material. The present results noticeably improve the wavenumber line list in the HITRAN 2016 data base.