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 H12 based on the measurements. Calculations are performed both with and without taking into account the phenomenon of rotational coupling.