It is impossible to directly measure the photoelectron spectrum of an atom using conventional XPS due to its low detection sensitivity. In this work, an indirect method has been developed to determine the binding energy (BE) of an atom. In this method, the BE of the atom can be obtained by extrapolation of the experimental BE curves with atomic deposition coverage to zero coverage. With this method, the Ni 2p3/2 BE's of atomic Ni on TiO2(001) and (110) surfaces are deduced to be 853.69 and 853.55 eV, respectively. Compared with atomic Ni in gas phase, relaxation shifts of 7.34 and 7.48 eV are obtained on TiO2(001) and (110) surfaces, respectively. These values are very close to the relaxation shift of 7.3 eV due to d electron screening, indicating d-like screening effects from the TiO2 substrates after Ni 2p photoionization. This method is also used to determinate the Ni 2p3/2 BE's of atomic Ni on TiO2(001) with different surface stoichiometries. The difference of Ni 2p3/2 BE is due to different interfacial charge transfer. Copyright © 2010 John Wiley & Sons, Ltd.