The electronic structures of norbornyl derivatives unveil their distinctive properties, with core electrons playing a pivotal role in shaping the molecule's characteristics. Core electrons, situated near the nucleus, contribute significantly to the total electronic energy of a molecule, dominating approximately 90% of it. They influence the overall electron density distribution within the molecule, which is particularly crucial in strained hydrocarbons where bond distortions are common, impacting stability and reactivity. Strained hydrocarbons often exhibit non-linear or distorted bond angles due to inherent strain, with core electrons influencing steric interactions among atoms and functional groups, thereby affecting stability. Moreover, the presence and arrangement of core electrons affect the electronic structure, thus impacting stability. For example, electron-donating or withdrawing groups can alter strain energy by modulating electron density around strained bonds. X-ray photoelectron spectroscopy (XPS), also known as electron spectroscopy for chemical analysis (ESCA) [63], is a powerful technique for studying core electrons. Travnikova et al. demonstrated at the French synchrotron Soleil that the C1s spectral bands of ethyl trifluoroacetate in ESCA can be resolved up to 3.1 eV due to distinct chemical environments .