Surface Probing Nitric Oxide Interactions with Metal Ions in Zeolites

2 Surface Probing Nitric Oxide Interactions with Metal Ions in Zeolites 

Lunsford [3b] and Hoffman and Nelson [23] first reported the ESR spectra for adsorbed NO molecules. Then, Kasai [4b] revealed that ESR spectra of NO probe molecules are very sensitive to the interaction with metal ions and Lewis acid sites in zeolites. The earlier ESR studies of the NO/zeolite system have been summarized in several review papers [3a, 4a, 8]. A number of ESR studies have been also carried out for NO adsorbed on metal oxides such as MgO and ZnO as reviewed by Che and Giamello [5]. Modern ESR techniques such as pulsed ESR [25-27], ENDOR (Electron Nuclear Double Resonance) [26], and multi-frequency (X-, Q-, and W-band) ESR [28] are especially useful for an unambiguous identification of the ESR magnetic parameters (g, hyperfine A, and quadrupole tensors, etc.) and, consequently, for a detailed characterization of structural changes and motional dynamics involved. Some recent advancements in ESR studies on NO adsorbed on zeolites are presented in this section. 

The decomposition of nitric oxide, a process in which NO is converted to harmless nitrogen and oxygen, deserves considerable practical attention, as the oxides 

The NO molecule exhibits the degenerate molecular orbitals, 2pir (x,y), in the ground electronic state, see Fig. 6.2. The orbital degeneracy can be lifted by the 

To evaluate accurate values of parameters E, A and /, three principal values of gxx, gyy and gzz have to be determined with a high degree of accuracy. The 

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