Abstract: The Auger spectra of PMo_12-x V_x and PMo_12-xW_x have been studied.A relationshipbetween OKL₂₃L₂₃ spectra and electron densities of oxygen in these heteropolyacids(HPA)was observed.It is found that the mobility of protons in HPA depends mainly upon thenegative charge of the oxygen atoms; the larger the kinetic energy for OKL₂₃L₂₃, i.e.thelarger the magnitude of the negative charge on the oxygen atoms, the stronger the bindingenergy to proton, and the smaller the proton mobility and hence the less acidity.InPMo_12-xV_x the kinetic energy of OKL₂₃L₂₃ increases with the increase of x value, but itdecreases with the increase of x in PMo_12-xW_x.The acidity of HPA is inversely related tothe kinetic energy of O KL₂₃L₂₃ Auger transition.

Key words: heteropolyacid, Auger spectrun of oxygen, P-Mo-heteropolyacids, P-W-heteropolyscid, X-ray photoelectron spectroscopy