Note that the computed max. CLS is not equal to the Δ B.E. observed in experiments, as indicated in Figure . In reality, given typical peak linewidths and resolution, the signal from O atoms with similar CLS are actually indistinguishable and would be experimentally identified as one peak. And Δ B.E. is the energy difference of two distinguishable peaks, which is smaller than max. CLS. Whether Δ B.E. can be observed in experiments depends both upon the energy interval of the two peaks and the instrumental linewidth. Figure shows the simulated O1s spectrum according to Figure with a linewidth of 0.3eV.