The NH and ND stretching fundamentals of ¹⁴$ND2H$

High resolution (0.004 cm⁻¹ instrumental bandwidth) interferometric Fourier transform infrared spectra of $N14D2H$ were obtained on a BOMEM DA002 spectrometer under essentially Doppler limited conditions. We report the analysis of the ND and NH stretching fundamentals of $N14D2H$ with term values for the symmetric (s) and antisymmetric (a) sublevels with respect to the inversion plane of the planar geometry $Tv (s)=2430.7990(7) cm−1$ and $Tv (a)=2434.6222(8) cm−1$ for the $ν3a$ fundamental, $Tv (s)=2559.8069(8) cm−1$ and $Tv (a)=2559.9630(9) cm−1$ for the $ν3b$ fundamental and $Tv (s)=3404.238(5) cm−1$ and $Tv (a)=3404.316(5) cm−1$ for the $ν1$ fundamental. The two modes $ν3$ which are degenerate in $ND3$ and whose degeneracy is lifted in $ND2H,$ are distinguished by the subscripts $3a$ or $3b,$ being symmetric $(3a)$ or antisymmetric $(3b)$ with respect to the $Cs$ plane of symmetry of the equilibrium geometry of $ND2H.$ Up to 20 molecular parameters of the effective S-reduced Hamiltonian could be determined accurately for each fundamental. In particular, the inversion-rotation interaction parameter could be determined for the two ND-stretching modes. Assignments were established with certainty by means of ground state combination differences. The results are important for the mode selective inhibition or catalysis of inversion at the nitrogen atom by exciting ND and NH stretching vibrations, for treatments of isotope effects on inversion of ammonia by means of effective Hamiltonians as well as true molecular Hamiltonians on high dimensional potential hypersurfaces.