Knowledge Bank

The absolute infrared intensities of the bending vibrations of $NH3$ and $PH3$ have been measured using the Wilson-Wells extrapolation method. In the case of the $A1$ mode in $NH3$, the band intensity was obtained by a study of some individual rotation lines. The observed intensities are used to calculate ""infrared bond moments"" for the N-H and P-H bonds in the different vibrations. The relation of these moments to each other and to the equilibrium molecular charge distribution is discussed in terms of a simple orbital-following model which permits changes in hybridization to occur during vibration.