Ionic fragmentation caused by Si: Is photoionization of 1-trifluorosilyl-2-trimethylsilyiethane [F3SiCH2CH2 Si(CH3)(3)] vapor was studied by the energy-selected photoclectron photoion coincidence method and monochromatized synchrotron radiation. In the Is photoionization at the Si atom bonded to three F atoms, H+ exceeded the other ions in the peak height, and production of SiF3+ ion seemed to be reduced. On the other hand, the Is photoionization at the other Si atom bonded to three CH3 groups enhanced production of H+ ion with high kinetic energy. These results suggest that Si:1s photoionization causes site-specific fragmentation. (c) 2005 Elsevier B.V. All rights reserved.