INDUCED INFRARED-ABSORPTION OF MOLECULAR-OXYGEN SORBED IN EXCHANGED A-ZEOLITES .2. FREQUENCY-SHIFT CALCULATION

O-2 sorbed in NaA, NaCaA, and CaA exhibits induced infrared bands whos e frequencies are differently shifted with respect to the gas phase fr equency. In the preceding article, we analyzed the intensity of these bands. The shift depends on the molecule-zeolite interaction, by the v ariation of the latter with respect to the normal coordinate of the mo lecule. We have calculated this interaction, to determine the adsorpti on sites of O-2 in these zeolites. It was shown that the main adsorpti on site in NaA is in front of the Na-III cation. The oxygen molecule c an take two orientations, parallel and perpendicular, with respect to the field of the Na+ cation. In NaCaA the adsorption site is in front of a Na+ or Ca2+ cation in a site S-1. It was shown that the frequency shift depends strongly on the location of the cation in the 6-ring. I n CaA, the strongest site seems to be located near a Ca2+ cation in a S-II site in a 8-ring window. The frequency shifts, calculated for all these adsorption sites, depend strongly on the variation of the quadr upole moment and of the parallel and perpendicular polarizability comp onent of the admolecule with respect to the normal coordinate, which a re only known up to first order. By adjusting the computed shift to th e experimental one, we have been able to calculate a crude value of th e second derivative of these molecular quantities with respect to the normal coordinate.