Beweglichkeit von Einfach- und Cluster-Ionen in Argon bei hohen Drucken

Abstract

A time-of-flight technique is used for the measurement of positive ion mobilities in argon in the 1–100 atm pressure range at 300 °K. The ions are produced by photoionization of gas atoms in the drift region with ultraviolet light from a spark discharge.

A mobility is found which varies continuously with the reduced electric fieldE/p ₀ and which exhibits two saturation values at 1.55±0.01 cm²/volt sec (forE/p ₀≳ 2 volt/cm torr) and at 0.818±0.003 (forE/p ₀≲ 0.17). The former value is in excellent agreement with the zero-field mobility obtained by Beaty for Ar⁺. The last value is interpreted in terms of the Langevin theory and connected with the formation of the Ar ⁺₃₃ labile cluster. This has the Ar⁺ ion as nucleus and is surrounded by two complete shells of 12 and 20 argon atoms respectively. A mean value of the cluster radius is estimated as 6.24 Å.