Resonanzeinfang langsamer Elektronen in Äthan und Propan

Abstract

Abstract By means of a time-of-flight method the electron drift velocity ν_ in ethane was measured at densities between N = 1,5 · 1019 and 1,1 · 1021 cm-3 (450 Torr ≦p20 ≦ 33390 Torr). Below E/N = 10-18 and above E/N = 10-16 Vcm2 (E/p20 < 0,03 and > 3,3) ν_ is independent of density N, in the intermediate region ν_ decreases at a given E/N with increasing density. This means a violation of the similarity rule. As function of E/N at a given X the relative drift velocity q = ν_ (p)/v (450 Torr) shows a resonance curve with a minimum at E/N = 6,5 · 10-18 {E/p20 - 0,2). This effect can be described, assuming that the electron is attached to the C2H6- molecule for a short time τ. The cross section for the electron attachment, Qa, has a resonance maximum at electron energies of ~ 80 meV. Qa is shown to be ≦ 10-15 cm2 and the life time to be ≦ 10-14 sec. - In propane a similar density-effect is found.