Ionization in Hydrogen by Fast Hydrogen Neutrals

Abstract

RECENT work by Varney and his collaborators^1,2,3, also earlier work by Beeck⁴, have shown that gases can be ionized by their own accelerated neutral molecules or atoms. A classical theoretical treatment of the problem was given by Zwicky⁵, who showed that the effect is most likely to occur when both reacting particles are of equal mass. It was first noticed with the inert gases, particularly argon, for which the effect is relatively large. Berry³ has very recently published results obtained with hydrogen in the type of apparatus developed by Varney's school, in which a velocity selector is used for the positive ions. The latter are neutralized in a separate chamber and then pass into the space-charge detector^6,7, where they are detected after causing ionization. The strength of the remaining neutral beam was assessed by measuring the secondary electron emission from a target by which it was struck. The voltage range for the neutral particles was approximately 900–6,400, and the cross-sections (N₁σ) per cm.³ of gas at 1 mm. mercury pressure were approximately 2(A), 0.05 (He), 0.15 (H₂) and 0.9 (N₂).