FRAGMENTATION OF F3SICH2CH2SI(CH3)(3) VAPOR FOLLOWING SI-2P CORE-LEVEL PHOTOEXCITATION - A SEARCH FOR A SITE-SPECIFIC PROCESS IN COMPLEX-MOLECULES

Site-specific excitation and fragmentation following Si:2p photoexcita tion 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. I n contrast to Cl3SiSi(CH3)(3) and F3SiCH2Si(CH3)(3), the occurrence of different chemical shifts for the two Si sites (site-specific excitat ion) is clearly revealed in the total photoionization efficiency curve of FSMSE. The site-specific fragmentation is moderately observed in t he mass spectra and occurs selectively around the Si atom where the ph otoexcitation has taken place. It is considered that the site-specific excitation and fragmentation are observed in molecules in which the t wo Si sites are located far from each ether and, thus, electron migrat ion between the two Si-containing groups [SiF3 and Si(CH3)(3)] is not effective. Published by Elsevier Science B.V.