## METHODS=A08-m3 |

Atomic beam techniques are used to measure the experimental differential cross sections of the chemi-ionization in sodium atom-iodine atom collisions in the electronvolt range.

We interpret the experimental methods thus obtained using the following theoretical methods
. We try to explain this chemi-ionization process by means of a semiclassical atom-atom model for ion-pair formation, which is based on transitions between electronically coupled states of the system, in particular Landau-Zener transitions.
In addition, the phenomenon of rotational coupling is taken into account.
The differential cross sections are calculated, from the states of the system, *via* the deflection function, using the stationary phase approximation, the uniform approximation and JWKB phase shifts
.