Nitrogen and oxygen core excitations in solid NaNO2 studied by X-ray absorption and resonant photoemission

The origin and properties of the nitrogen and oxygen K excitations in solid NaNO2 were investigated combining high-resolution X-ray absorption and res onant photoemission spectroscopy. The absorption spectra obtained were trea ted on the basis of comparison between the spectra of solid NaNO2 and gas-p hase NO2 and CH3NO2 molecules, as a result of which main absorption bands w ere assumed to be associated with the core electron transitions to unoccupi ed pi and sigma molecular orbitals of the planar NO2Na quasimolecule - the structural unit of the crystal. Examining series of the photoemission spect ra taken at the NK and OK edges, it was found that the pi and sigma excitat ions decay in different ways: three decay channels (spectator, participator and normal Auger processes) were observed for the pi excitations whereas o nly the normal and spectator Auger decay channels were seen for the sigma e xcitations. This fact was qualitatively explained in terms of differences i n the spatial localization and lifetime of the corresponding core excitatio ns. The results of the resonant photoemission study give a direct evidence for the quasimolecular NO2- origin of the lowest unoccupied electronic stat es of the pi type in solid NaNO2. (C) 1999 Elsevier Science B.V. All rights reserved.