FAST NEGATIVE HYDROGEN IONS

Abstract

A proton beam was directed through hydrogen gas at low pressure and magnetic analysis of the emergent beam showed that an appreciable fraction of the beam was transformed into negative hydrogen ions. After the beam had traversed a sufficient layer of gas, the ratio of negative hydrogen ions to protons reached an equilibrium value which was a maximum of 22.2% at 8.5 kev. The proton energy interval investigated extended from 4 to 70 kev.In this interval the electron loss cross section for negative hydrogen ions was measured and found to vary from 6.3 × 10−16 sq. cm. at 4.2 kev. to 2.5 × 10−10 sq. cm. at 70.3 kev. The electron capture cross section for protons in hydrogen was measured over the same interval and the results agreed substantially with those of other workers. The electron capture cross section for neutral atoms was also determined by combining present results for the negative ion loss cross section and for the equilibrium ratio of H− to H+ with the values of Bartels and of Montague and Ribe for the ratio of neutral atom loss cross section to the proton capture cross section.