Experimental confirmation of quantum monodromy: The millimeter wave spectrum of cyanogen isothiocyanate NCNCS

We have made energy-momentum maps for the experimental end-over-end rotational energy and the two-dimensional bending vibrational energy, both of which confirm the dominating effects of nontrivial quantum monodromy in cyanogen isothiocyanate. Accidental resonances in the rotational spectra yield accurate intervals between bending states.