There is also a large, broad hydrogen bonded NH stretching anharmonic feature spanning 2700-3250 cm -1 , which is typically ignored since harmonic calculations cannot accurately reproduce this region. We performed calculations and then compared these computed spectra to the experimentally collected spectrum in order to identify key spectral features, that could then ideally be tracked in larger clusters. Both calculations are very close in energy to each other, essentially isoenergetic, and their energy difference is within the error of the calculation. From an energetic standpoint, its possible that both of these isomers exist in experiment. Neither calculation appears to capture the experimental spectrum particularly well, most notably in the free NH 2 stretching region, as well as, in the NH 2 bending/wagging region. In the experimental spectrum there is splitting in the free NH 2 symmetric stretching region that suggests the presence of isomers, whether they be structural isomers or tag isomers. In Figure , both untagged calculations along with all possible tag location calcu-lations are compared to the experimental (1, 0, 1) spectrum. The tag calculations appear to drastically enhance the relative free NH stretching intensities, whereas in the experimental spectrum, there is not an evident intensity enhancement in this region. Although it is possible that tag effects could emphasize differences between the calculated and experimental spectra, it is likely not the only source of the spectral discrepancies in this case, as none of the NH 2 mode relative intensity patterns are captured any more closely in the the tagged calculated spectra (Figure ). However, if we observe Figure in the supplemental information, with the overlay of the two (untagged) calculated spectra, it shows that it is highly likely that both isomers exist experimentally, as the overlayed spectra more closely captures the spectral features in the free NH 2 stretching region and the relative intensity pattern of the NH 2 bending/wagging modes in the fingerprint region are more appropriately reproduced.