Fragmentbildung und Ionenausbeute der Tetramethylverbindungen von Si, Ge, Sn und Pb in Abhängigkeit von der Elektronenstoßenergie im Massenspektrometer / Fragmentations and Ion Yields of the Tetramethyl Compounds of Si, Ge, Sn and Pb in Dependence of the Electron Impact Energy in a Mass Spectrometer

Open Access
Publisher Website
Google Scholar
Abstract
In this study the behaviour of the tetramethyl compounds of Si, Ge, Sn and Pb in an ion source was investigated by mass spectrometry under equal conditions. A systematic investigation of the fragment formation and of the ion yield as a function of the electron impact energy and the atomic number of the central atom in the tetramethyl compounds was carried out. In all cases the trimethyl ions show the highest intensity in the whole energy range from 15 to 100 eV electron impact energy. At an electron impact energy of 20 eV the number of peaks having a high intensity in the mass spectrum is rather small. The relative stability of the trimethyl ions can be ascribed to their even electron number. Besides, the trimethyl ions are isoelectronic with the trivalent compounds of the III A group. The decreasing intensity of the trimethyl ions and the increasing intensity of the monomethyl ions with higher atomic number of the central atom can be explained by the increasing stability of the lower oxidation state. The ion yield of the sum of all fragments containing a metal atom reaches a maximum in the case of Ge(CH3)4 and decreases from Ge(CH3)4 to Pb(CH3)4. The tendency of the ion yields of the metal containing fragments is parallel to the values of the electronegativities calculated by ALLRED and ROCHOW. The tendency of the ion yields and the localization of the positive charge after the ionization are discussed in detail.

This publication has 0 references indexed in Scilit: