Evidence of very strong [2x nu(NO)] overtones when adsorbing NO in Cu-I,Cu-II-exchanged Y zeolites

In this communication the first vibrational results obtained in "transmission" mode, concerning NO/Cu-Y systems, containing Cu-I and Cu-II ions, are presented. The IR spectra of these systems are characterized by strong and well defined IR peaks, both in the v(NO) and 2 x v(NO) stretching regions. Plausible physical reasons justifying the unusual and astonishing high intensity of the peaks in the 2 x v(NO) overtone region are discussed.