The chemical environments of norbornyl derivatives NBA, PPL, and QC are notably similar, as they all possess single C-C bonds, leading to closely located C1s Core Electron Binding Energies (CEBEs), as depicted in Figure . However, despite this proximity, the specific locations of their C1s CEBEs differ due to their structural disparities. For instance, in NBA, the C1s CEBE of the flag carbon C7 is the smallest, whereas in QC, it is closely located to the bridge carbons C1 and C4 but larger. Conversely, in PPL, the CEBE of this carbon becomes the largest among the C1s energies. The C1s energy order of QC aligns more closely with that given by Nunes et al . In their model fitting of C1s CEBE from small molecules using XPS measurements, Haiduke et al