Experimental and theoretical investigations of the X-ray absorption near edge spectra (XANES) of P4O6 and P4O6X (X  O, S, Se) Original Research Article

The phosphorus oxide cage compounds P4O6 and P4O6X (X  O, S, Se) were investigated by X-ray absorption near edge spectroscopy (XANES) and by calculations of inner-shell excited states using a recently developed method which combines density functional and single-excitation configuration interaction methods (DFT/SCI). For an interpretation of the shape and energy positions of the observed resonances, XANES spectra were compared with those of the reference compounds P(OPh)3 and X  P(OPh)3 which have a similar first coordination shell at the phosphorus atoms. On the basis of the theoretical results a complete assignment of the three resonances observed below the ionization potential could be made. Valence orbital relaxation effects and transitions to Rydberg states not considered thus seem not to play an important role for the interpretation of the spectra. The influence of the characteristics of the unoccupied orbitals on the locations and intensities of the 1s transitions of the phosphorus atoms in oxidation states +III and +V are discussed.