Experimental XANES spectra are characterized by a σ * (C-C) resonance splits from a broad peak to narrower peaks with increased strain, while the tertiary σ * (C-H) peaks are broader for cubane with a shift to lower energies. These essential near-edge features are well reproduced by CAM-B3LYP/CIS calculations [Fig. ], although the higher-energy peaks in cubane are shifted a bit too high in energy. TD-CAM-B3LYP spectra show similar features but require a shift of 11 eV to match experiment, as compared to 4 eV for CAM-B3LYP/CIS. Theoretical spectra for both adamantane and twistane spectra show an intense feature around 290 eV, similar to that observed in various saturated hydrocarbons. The shift relative to the K-edge is accurately reproduced by the CAM-B3LYP/CIS calculations. The largest differences between theory and experiment are observed for cubane, where two lower-energy features that are present around 287 eV for adamantane and twistane, which are are not resolved in the simulated spectrum for cubane. (These features are associated with tertiary carbons and methylene groups, respectively. 108 ) The singular peak that is obtained for cubane is more intense than the leading x-ray absorption features for adamantane or twistane, suggesting a pair of peaks who splitting is smaller than what is observed experimentally.