Some experiments in positive ion kinetics

Mean free path and mean energy loss per collision of positive ions of potassium and caesium in helium, neon, argon, hydrogen and nitrogen.—The motion of certain positive ions through gases was investigated in an experimental tube of simple design. The ions were obtained from the potassium and caesium catalyst sources developed at the Fixed Nitrogen Laboratory, and their behavior was studied in helium, neon, argon, hydrogen, and nitrogen. It was found that the results were best explained on the basis of a free path approximately equal to the kinetic theory value, and on an average fraction of energy lost per collision considerably less than would be expected on ordinary considerations. It is suggested that the explanation of this is to be found in a more accurate consideration of the fields of force involved at these encounters.