Electron spin resonance spectra of nitric oxide adsorbed on zeolites

Electron spin resonance (e.s.r.) spectra of NO adsorbed on the 4 zeolites Linde 4A, 5A, 13X, and hydrogen mordenite were measured at 77°K. No e.s.r. signal was observed for NO on silica gel. By use of expressions for the line shapes of polycrystalline samples, assuming axially symmetric g-tensors, and taking into account also isotropic coupling, values of [Formula: see text] and line width were derived by an iterative procedure. From these, the crystal field splitting, Δ, of the 2pπ levels, which become non-degenerate on adsorption, were calculated. By relating Δ to the interaction of the non-axial components of the quadru-pole moment with the corresponding electric field gradients, the non-axial component of the latter is estimated for the surface fields of the zeolites.