Group theory is often used by chemists to assist in the interpretation of infrared spectra. For example, there are four N-H bonds in NH4 +, with four stretching modes possible, where each is a linear combination of the four stretching modes and each has a symmetry. There is a possibility that several vibrational modes occur at the same frequency, and are therefore degenerate.
(a) In the case of the tetrahedral ion NH4 +, is it necessary to consider the possibility of degeneration? Is it possible that degeneration occurs in any of the vibrational frequencies of NH2D2 +?