Induced IR overtone and fundamental bands of isotopic H 2 molecules adsorbed in NaCaA zeolites

Abstract

NIR spectroscopy has been successfully applied to surface chemical problems, using the FT transmission technique. Vibrational spectra of H 2 and D 2, adsorbed in NaA and NaCaA zeolites, have been recorded in the fundamental regions of both adsorbates and, for the first time, in the overtone region of D 2. Useful information on the properties of the adsorbed molecules can be derived from the overtone spectra of D 2 and the fine structure of the H 2 fundamental. It turns out that the properties of the D 2 molecules, e.g. dissociation energy and anharmonicity, are hardly affected by adsorption. The fine structure of the H 2 fundamental, however, indicates the rotation to be strongly hindered. The ortho-para splitting is decreased with respect to the free molecule value and approaches that for planarly rotating molecules. Due to this hindrance, the corresponding D 2 splitting is not resolved.