## Central problem=A08-m2b |

In order to test the semiclassical calculation method and to test the suitability of the Landau-Zener theory for chemi-ionization in collision processes , the collision process is studied .

For that purpose, relative differential cross sections are measured for the atom-atom collision process at kinetic energies from 13 to 85 *eV*, using atomic beam techniques
allowing for the experimental resolution of interferences of two types, *viz.* the rainbow structure and the Stueckelberg oscillations
.

The measurements are then compared with semiclassical differential cross sections for the chemi-ionization calculated
*via* the deflection curves, the Landau-Zener transition probability, the stationary-phase approximation and JWKB phase shifts, using estimations of the covalent potential parameters and the pseudocrossing parameter *H _{12}* based on the measurements. Calculations are performed both with and without taking into account the phenomenon of rotational coupling.