The ∆ k = ±2 perturbation-allowed ν4 band and inversion-rotation energy levels of 15NH 3

More than 800 ∆ k = ±2 and 60 ∆ k = ±3 forbidden transitions to the ν₄ and 2 ν₂ vibrational levels, respectively, have been assigned in the Fourier transform spectra of ¹⁵NH ₃, recorded with a pathlength of 96 m. Combination differences derived from these transitions provide information on the spacing between the ground state energy levels with different rotational quantum numbers K in the interval from 0 to 16. These data along with wavenumbers of all the available allowed transitions pertaining to the ground and ν₂ states have been subjected to a simultaneous least-squares analysis using two different parametrization models to obtain precise values of the inversion-rotation energy levels.