This constituent module contains (in the beginning) a brief summary of the mesoscopic account of the atom-atom model, tailored to the specific situation: what are the coupled states.
The ionic potential of NaI is said to be well-known; the covalent potential is determined in the Interpretation module m5. However, the general features of the potential are part of the theoretical toolbox, because they do not depend on the new measurements.
In the original article, the approximations are listed in the 7.Discussion section. We also summarised them as the restrictions of the Theoretical methods in this module.
The original Introduction contained some discussion about the applicability of the semiclassical LZ model to the differential cross section of chemi-ionization of Na+I. The rest was presented in section 3.Potential curves. The last part of that section, however, describes and discusses the specific potential curve that has been determined in this work. In the modular version, we give an account of how the potential parameters have been determined in the Quantitative interpretation module A08-m5bi and also provide the resulting potential in the Treated results module A08-m4bii1.
It has been assumed that the species of the relevant states are known or can be determined independently of the experimental results. If this is not the case, the information about the species would belong in the Interpretation.
The LS-coupling is the spin-orbit coupling in the lowest states of the NaI molecule, which is explained in textbooks on molecular spectroscopy.
The terms radial coupling, translational coupling, electronic coupling and Landau-Zener coupling are used as synonyms.
After this module on the Landau-Zener coupling, the essay-type path avoids the presentation of the rotational coupling and cuts to A08-m3cii, in which it is explained how differential cross sections can be calculated, given the coupling.