Nachweis metastabiler Ionen mit langen Lebensdauern

Abstract

In order to search for metastable ions with long lifetimes hydrocarbon molecules are ionized by electron impact and the fragment ions preselected by a magnetic spectrometer. Subsequently these selected ions M₀ ⁺ pass a drift tube where they may decay into ions M^{1 +}, Μ₂ ⁺, .... Behind the drift tube a quadrupole spectrometer is used to analyze the ion current for its mass components M₀ ⁺, M₁ ⁺ For selected species of fragment ions M₀ ⁺ of n-butane, n-pentane, and n-hexane it was found that between 10% and 20% of M₀+ decay in the time interval of 10 μs to 150 μs after ionization. Furthermore, 150 μs after ionization (0.040 ± 0.025) % of mass 86⁺ ions from n-hexane decompose into 56⁺ fragment ions per 1 μs.