The topology of the reaction stereo-dynamics in chemi-ionizations

Chemi-ionizations occur in interstellar media as well as in flames and plasmas with two elementary reaction mechanisms. Here, the authors propose an optical potential formulation to describe the topology of prototypical chemi-ionization reactions of excited state neon with argon, nitrogen and ammonia molecules. Details on the stereo-dynamic topology of chemi-ionizations highlight the role of the centrifugal barrier of colliding reactants: it acts as a selector of the orbital quantum number effective for reaction in a state-to-state treatment. Here, an accurate internally consistent formulation of the Optical interaction potentials, obtained by the combined analysis of scattering and spectroscopic experimental findings, casts light on structure, energy and angular momentum couplings of the precursor (pre-reactive) state controlling the stereo-dynamics of prototypical chemi-ionization reactions. The closest approach (turning point) of reagents, is found to control the relative weight of two different reaction mechanisms: (i) A direct mechanism stimulated by exchange chemical forces mainly acting at short separation distances and high collision energy; (ii) An indirect mechanism, caused by the combination of weak chemical and physical forces dominant at larger distances, mainly probed at low collision energy, that can be triggered by a virtual photon exchange between reagents.

Automated summary

The authors propose an optical potential formulation to describe the topology of prototypical chemi-ionization reactions of excited state neon with argon, nitrogen, and ammonia molecules. The stereo-dynamic topology of chemi-ionizations is related to the centrifugal barrier of colliding reactants, which acts as a selector of the orbital quantum number effective for reaction in a state-to-state treatment. The accurate formulation of the Optical interaction potentials obtained by the combined analysis of scattering and spectroscopic experimental findings sheds light on the structure, energy, and angular momentum couplings of the precursor state controlling the stereo-dynamics of prototypical chemi-ionization reactions.