The relative differential cross sections for chemi-ionisation of the systems K + BR2 at initial relative kinetic energies of 10.35 and 6.9 eV, K + I2 at 11.15 eV and Li + BR2 at 6.25 eV have been measured in molecular beam experiments .
The general shape of the measured cross sections can be explained qualitatively using a classical atom-atom-Zener model, via the general shape of the deflection function . A classical explanation suffices, except for small angles, where a quantum explanation is necessary .
The relative differential cross section has been calculated for the inelastic-collision process K + Br2 K+ + (Br + Br-) . The calculation is based on a simple classical model, using impact-parameter approximation, an isotropic intermolecular potential and neglecting the internal states of the X2 molecule , and based on the potential of the system which has been determined via fitting.
These measurements do seem to be suitable for the determination of potential parameters, crossing distance and resonance energy at the crossing point .
However, the classically calculated differential cross sections are only in qualitative agreement with the measurements . Quantative agreement is poor, because the assumed simplifications of an isotropic potential and the absence of internal state are invalid for the systems at hand.
Thus, in answer to the central question of this article , the differential cross section of chemi-ionisation of alkali halides have been measured and explained qualitatively using a simple classical system, but a quantitative explanation of the reaction dynamics has not been found.