The Effective Cross Section of Positive Alkali Ions with Respect to Gas Molecules

Abstract

The absorption of positive sodium ions with velocities of 40 to 400 equivalent volts has been studied in hydrogen, nitrogen and oxygen. The nature of the collision processes has, in each case, been studied to determine the relative importance of neutralization, retardation or small angle scattering. The mean free paths and effective cross section of the sodium ions with respect to the gas molecules is found to be a function of the pressure of the gas, the velocity of the ion and the nature of the gas-ion combination. The effective cross section of each gas-ion combination approaches the kinetic theory value at low velocity of the ion while at high velocities it approaches a minimum considerably smaller than the kinetic theory value. At any given velocity over the range studied, the effective cross section of the gas-ion combination increases in the order hydrogen, nitrogen, oxygen. The values for nitrogen and oxygen are essentially, within experimental errors, equal. An improved furnace for the production of positive ions has been developed.