Eine Methode zum Nachweis langsamer Elektronen aus der Anregung und Ionisation von Molekeln durch Elektronenstoß

Abstract

A new type of secondary negative ions was found in mixtures of “indicator-compounds” such as methyl iodide and sulfur hexafluoride with sulfur dioxide, carbon disulfide, xenon and many other substances. It is shown that the precursors of these secondary ions are free electrons of low kinetic energy which are produced in collisions of fast electrons with gas molecules. For example, sulfur dioxide was found to possess three discrete levels between about 2 and 8 eV which are frequently excited by electrons according to SO2+ e–→ SO2* + e0 –, where the electron e0 – has nearly no kinetic energy and therefore is readily captured by an indicator molecule. Similarly, slow electrons were found to be formed in various excitation and ionization processes (including double and triple ionization) in xenon. This “indicator” method may generally be used to study excitation and ionization processes in which slow electrons are produced.