The high resolution spectrum of 15NH3 in the far-infrared: Rotation-inversion transitions in the ground, v2=1, 2 and v4=1 states

Abstract The high resolution spectrum of 15 NH 3 has been recorded at unapodized resolution of 0.00096 cm −1 in the region 60–600 cm −1 using the Bruker IFS 125 Fourier transform spectrometer located at the far-infrared beam-line, Canadian Light Source. We report on the observation and analysis of the rotation-inversion spectrum in the ground, v 2 =1, 2 and v 4 =1 states. All the rotation-inversion transitions in the ground state together with the pure inversion transitions present in the literature were fitted simultaneously on the basis of a rotation-inversion Hamiltonian which includes distortion constants up to the 12 th power in the angular momentum and the Δ k =±3 and Δ k =±6 interaction terms. A set of effective parameters was also obtained for the v 2 =1 state adopting the same theoretical model. For the v 2 =2 and v 4 =1 states only a list of observed transitions is reported. The wavenumbers of all the assigned transitions were compared with their theoretically predicted values [S.N. Yurchenko, J. Quant. Spectrosc. Radiat. Transf ., 2015, 152 , 28]. The present results noticeably improve the wavenumber line list in the HITRAN data base [L. S. Rothman et al. J. Quant. Spectrosc. Radiat. Transf. ,2013, 130 , 4].