ON ANALYTICAL EXPRESSION OF IONISATION CROSS SECTION FOR ATOM-ATOM COLLISIONS AND ON ION-ELECTRON RECOMBINATION IN DENSE NEUTRAL GASES

Thomson's classical theory for the calculation of ionisation cross sections in electron-atom encounters is applied for calculating the ionisation cross section for atom-atom collisions. A very simple formula is obtained permitting a rapid calculation of the total ionisation cross sections as a function of the kinetic energy Ea and the mass mA of the ionizing atom, and of the binding energy Ei and the number ξi of equivalent electrons in the electronic shell to be ionized. The formula is in good agreement with quantum mechanical calculations and with experimental results. It can be applied to ionization from ground and from excited states. From this formula one obtains an expression for the rate coefficient for ionization in the center-of-mass system of the colliding particles. Then, the method of detailed balancing is applied to calculate the rate coefficient for ion-electron three-body collisional recombination with a neutral atom acting as the third body. This latter formula is applicable to recombination into the ground and into excited states. © 1968 Springer-Verlag.