Pseudo-selection rules for rotational transitions between two NH₃ inversion doublets belonging to the same K-ladder, when vibrational excitation is involved. Parities are given on the right hand side. Excitation into a vibrationally excited level and subsequent decay leads to ΔJ = 0,  ±1, and  ±2 pseudo-transitions without parity change in the ground state. Shown are two R-branch transitions with ΔJ = −1.