Data for: Test of the Validity of Bragg´s Rule for Mean Excitation Energies

We are investigated the effect of chemical binding on the validity of Bragg’s rule for the calculation of stopping cross sections and mean excitation energies. As test cases we use a series of small molecules and molecular ions, primarily carbon and nitrogen halides. We find that neglect of chemical binding nearly always reduces the mean excitation energies and that the fully atomic decomposition of any molecule but a diatomic molecule never gives the best fulfilment of Bragg’s rule. The best fulfilment of Bragg’s rule is obtained when as few bonds as possible are broken and when the choice of fragments is guided by chemical knowledge. By investigating several alternative fragmentation patterns for a molecule, guidelines for choice of optimal fragmentation are suggested.