Ionization and Excitation Processes in Argon, Krypton, and the C2Hydrocarbons Produced by Various Means

摘要

Multiple ionization produced in argon and krypton by 3.5hyphen;keV electrons is reported. The ionization mechanism is tentatively proposed to be similar to that known for nuclear transitions, namely, a combination of electron shakeoff with primary ionization in one of the innerhyphen;orbitalhyphen;electron shells (n=1 or 2) followed by Auger transitions.The relative proportions of fragment ions produced in the C2hydrocarbons by 3.5hyphen;keV electrons are also reported. These data bear a marked similarity to those obtained by the dissociative ionization of the C2hydrocarbons with 75hyphen;eV electrons. However, ions produced by 3.5hyphen;keV electrons retain excitation energy longer as is shown by their respective rates of intramolecular decomposition (metastable transitions). Despite the longer retention of excitation energy, the reaction rate for 3.5hyphen;keV electronhyphen;induced ions in ionmdash;molecule reactions is the same as that for 75hyphen;eV electronhyphen;induced ions. Reaction rates between neutral molecules and C2H4+ions from different parent molecules appear to be independent of the parent, thus suggesting that the ions, initially probably different in configuration, all rearrange to the same configuration before reacting.The fragment ion pattern produced in ethane by 50ndash;75hyphen;eV electrons is strikingly similar to that produced by either 3.5hyphen;keV electrons or by 5hyphen;MeV agr; particles. In ethylene, likewise, the fragment ion patterns produced by 5hyphen;MeV agr; particles, bgr; particles from Ni63, 3.5hyphen;keV electrons and 50ndash;75hyphen;eV electrons are quite similar. This lends some support to the common practice of using 50ndash;75hyphen;eV mass spectra to predict primary ion products in radiation chemistry.