The properties that are dependent on the core electrons are less well understood. Accurate calculations of the CEBE (XPS spectrum) in the core region rely heavily on the correct description of the core orbitals. In many applications, calculating the core electron spectroscopy can be computationally demanding and is not straightforward. The method used to calculate the CEBEs of the hydrocarbons in the present study is consistent with the method used in a previous study of ammonia borane (H3BNH3) and the dehydrogenated compounds H2BNH2 and HBNH . Briefly, based on the optimized geometries in the gas phase, CEBEs were calculated using the Δ(PW86x-PW91c/et-pVQZ) + Crel method . This method accounts for the energy difference with Vxc of PW86 for exchange and PW91 for correlation, along with an empirically determined relativistic effect term (Crel) which is approximately 0.05 eV for small to medium organic compounds . In the adiabatic C1s CEBE calculations, the geometry of the molecule cation was optimized, whereas for the vertical C1s CEBE calculations, the geometry of the molecule cation was identical to the ground state of the neutral molecule. This method calculates the vertical CEBEs of a molecule in the gas phase, which has been well benchmarked and has been employed to accurately produce CEBEs for a large number of compounds , in joint theory and synchrotron-sourced XPS measurement studies in the past decade .