None of the calculations were able to properly replicate the splitting of the higher energy peaks associated with the free NH and OH stretching modes above 3300 cm -1 in the experimental spectrum. As mentioned in the (1, 0, 1) discussion, this splitting usually implies the existence of experimental isomers. However, since both higher energy calculations (isomers B and C) can be eliminated due to their lack of structural arrangements linked to several experimentally present vibrational modes, we turn to the calculations including N 2 tags performed on isomer A in Figure to further interpret this splitting. There are three possible tag locations in this arrangement, and these include the free OH or one of the two free NHs. Upon comparison, these three tagged isomer spectra hint at the presence of isomers based on tag location, and not structural isomers. All three stretches (free symmetric NH 2 , free Figure : The experimental CIVP spectrum (top) is compared to the computed harmonic IR spectra (bottom) of the (1, 2, 0) cluster. The main features involve free OH stretching and bending modes (peaks in red), NH stretching and bending modes (peaks in blue) and IO stretching modes (peaks in purple). Isomer A is found to be the best match to the experimental spectrum as it contains both free OH and NH stretches and the fingerprint relative peak intensity pattern is well reproduced. Therefore isomer A is believed to be the experimentally present structure. asymmetric NH 2 , and free OH) exhibit splitting, and the presence of a very small red-shifted free OH stretching peak suggest that all three tag isomers exist in experiment.