Photoionization by Argon Resonance Lines

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Abstract
The direct and sensitized photoionization of ammonia and propane by argon resonance lines has been investigated. The ion current of direct photoionization approximately followed Beers law. The ratio of the absorption cross section of propane to that of ammonia was found to be 3.2. The ion current of sensitized photoionization generally increased with argon pressure. When the direct photoionization current was sufficiently large, however, the ion current decreased with increasing argon pressure, because the ionization induced by the energy transferred from the excited argon atoms is a competitive process of that induced by the photons absorbed by the sample molecules. From these results, it was concluded that the most important role of argon as a sensitizer is to increase the apparent absorption cross section of sample.