Role of Impurities in Thermal Ionization


THE mechanism of thermal ionization has received considerable attention in recent shock tube studies, mainly because of its importance in high speed, high altitude flight. At degrees of ionization below about 10−4, the dominant process involves atom–atom rather than electron–atom collisions1. Furthermore, the rate-determining step is usually the formation of the lowest electronically excited state of the atom. The presence of trace quantities of impurities with low ionization potentials greatly enhances the ionization rates and it has proved very difficult to eliminate such impurity effects1,2.

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BRADLEY, J., ROBINSON, P. Role of Impurities in Thermal Ionization. Nature 214, 1218–1219 (1967).

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