Chemical Reaction Control via the K Shell Excitation of Polyatomic Molecule

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Molecular size, sate, and shape effects on the specific fragmentation of the K shell excited polyatomic molecules were investigated for (a) triatomic O_3 and small molecules with methane-shape, (b) aromatics, and (c) aliphatic compounds. Synchrotron radiation was used for the soft X-ray source.Total photoabsorption cross section of ozone in the 0 K edge was first observed, In the small CF_3CN and CCl_3CN molecules, site specific fragmentation was weak or negligible in the C K, N K, and Cl L shell excitations. Auger electron spectra measured support the present observation. In aromatic compounds the phenyl group in a molecule decomposes characteristically and thus the initial memory excited was mostly lost, In the N and 0 K shell excitations of aliphatic CH_3OCOCN and CH_3OCOCH_2CN molecules, molecular size effect was clearly observed. That is, in CH_3OCOCN site dependent fragmentation was very weak while in CH_3OCOCH_2CN the fragment patterns were largely different between the N(1s) and O(1s) electron excitations. Site selective fragmentation was more evidently observed in the N and O K shell excitations of CH_3COCH_2CH_2CH_2CN in which five carbon atoms separate the interesting N and O atoms. Electronic state-specific fragmentation was observed in the pi*_<CN>*N(1s) resonance excitation of CH_3OCOCH_2CN and CH_3O(CH_2)_3CN in which N^+ and CO^+ fragment ions were exclusively produced.From the research results in the present study it might be expected that inner core excitation by using soft X-ray will be a useful tool for cutting a chemical bond in molecule such as a surgical knife in near future.