Double Impacts by Electrons in Helium

Abstract

IN a paper on the precise measurement of the critical potentials of gases (Proc. Roy. Soc., 107–291, 1925) Mr. E. G. Dymond finds that the difference between the first and second kink in the current potential curve in helium is 20.9 volts and not 20.55 volts as one would expect if the first kink corresponds to electrons which have caused the transition 1S–2s (type A), and the second kink to electrons which have caused two transitions 1S–2S and 1S–2s (type BA). In attempting an explanation he assumes that in his apparatus the second kink is due to the transition BB.