Fragmentation of F_3SiCH_2CH_2Si(CH_3)_3 vapour following Si:2p core-level photoexcitation. A search for a site-specific process in complex molecules

摘要

Site-specific excitation and fragmentation following Si : 2p photoexcitation of 1-trifluorosilyl-2-trimethylsilylethane (F3SiCH2CH2Si(CH3)3, FSMSE), in which two Si sites are separated by two -CH2- groups, have been studied in the vapour phase by means of synchrotron radiation. In contrast to C13SiSi(CH3)3 and F3SiCH2Si(CH3)3, the occurrence of different chemical shifts for the two Si sites (site-specific excitation) is clearly revealed in the total photoionization efficiency curve of FSMSE. The site-specific fragmentation is moderately observed in the mass spectra and occurs selectively around the Si atom where the photoexcitation has taken place. It is considered that the site-specific excitation and fragmentation are observed in molecules in which the two Si sites are located far from each other and, thus, electron migration between the two Si-containing groups [SiF3 and Si(CH3)3] is not effective. Published by Elsevier Science B.V.