The absorption of slow cathode rays in various gases

Recently a method has been developed whereby the total ionisation due to the absorption of slow cathode rays may be directly measured. The application of this method to measurements of the total ionisation in air was the subject of a previous paper. The present paper concerns its application to helium, argon, hydrogen, nitrogen, and carbon dioxide. A beam of electrons, all having the same initial energy, was introduced into an ionisation chamber containing gas at a given pressure. The incoming electron current and the ionisation current due to the passage of the electrons through the chamber were measured. The ratio ionisation current/electron current determined the average ionisation per electron. A detailed description of apparatus and procedure has been given previously. There follows a statement of the purity of gases used in the ionisation measurements.