Active control of chemical bond scission by site-specific core excitation

Core-electron excitation has a possibility to induce selective chemical bond scission due to its special localization and selectivity. Active control of chemical bond scission was examined in photon stimulated ion desorption (PSID) of core-excited poly-methylmethacrylate (PMMA) thin film, methyl ester terminated self-assembled monolayer (MHDA SAM), its partially;deuterated SAM (MHDA-d(3)) and ethyl ester terminated SAM (EHDA). Site-selective chemical bond scissions were observed for all molecular systems in the C1s resonant excitations as specific desorptions of CHn+, CDn+ (n = 1-3), and CZH (m = 2-5) ions for PMMA and MHDA, MHDA-d(3), and EHDA, respectively. Particularly, PSID of CHn+ (n = 1-3) ions observed at the sigma*(O-CH3) <-- C1s(OCH3) excitation of MHDA exhibits significant dependence on the incidence angle of synchrotron radiation light. The experimental results suggest that site-specific PSID by core excitation can be actively controlled by adjusting a molecular environment of a desorbing functional group and the direction of the electric field vector of the incidence light. (C) 2002 Elsevier Science B.V. All rights reserved.