An Absolute Determination of the Minimum Ionizing Energy of an Electron, and the Application of the Theory of Ionization by Collision to Mixtures of Gases

Edwin S. Bishop
1911 Physical Review  
T HE theory of "ionization by collision" has been very beautifully worked out by J. S. Townsend and verified by him and others 1 for various gases at low pressures. The orignial purpose of these experiments was to submit the theory to a more rigid test by extending the observations to wide ranges of pressure, and by predicting, if possible, the electrical properties of a mixture of gases, the properties of the constituent pure gases being known. Professor Townsend has shown that an ion in a
more » ... hat an ion in a sufficiently strong electric field will acquire sufficient kinetic energy between some of the collisions with the molecules to produce new ions from the neutral molecules. He has further shown that if the field strength is not too high, it is only the negative ion which is effective in producing new ones. Under these conditions, if we have no ions set free by the action of the ultra-violet light at the negative plate of the two parallel plates between which the electric field is established, then the number of ions n reaching the positive plate is given by the formula n = n 0 e ad (i) where e is Napier's base, a is the number of ions (either positive or negative) produced by the collisions of a negative ion in passing through one centimeter of the gas, and d is the distance between the plates in
doi:10.1103/physrevseriesi.33.325 fatcat:irpiqepvcnhrbcztmvbr5tlyvy