Abstract
This paper reports on the collision dynamics of N2 with metastable Ne* promoting chemiionizations, prototype of barrier-less oxidation reactions of great interest for fundamental and applied research. Extending guidelines presented in previous papers for the atom–atom case, an innovative treatment of the reaction stereodynamics involving molecules in a quantum state-to-state resolution conditions is proposed that emphasizes the role of structure and stability of the precursor that is here the reaction transition state. A critical test of such treatment, carried out exploiting a new formulation both of real and imaginary parts of the optical potential driving the reaction dynamics, is represented by the detailed-combined description of all relevant findings, provided by high resolution molecular beam scattering experiments carried out in our and other laboratories. The present analysis casts light on basic electronic rearrangements of such prototype oxidation reaction which are expected to be of fundamental interest for many other reactions involving open shell atoms and free radicals.
Highlights
This paper reports on the collision dynamics of N2 with metastable Ne* promoting chemiionizations, prototype of barrier-less oxidation reactions of great interest for fundamental and applied research
A new theoretical approach, proposed by us and applied to the atom–atom Ne*(3P2,0) + Ar, Kr and Xe reactions[14,15,16], pointed out that such Chemiionization reactions (CHEMI) occur via two different microscopic mechanisms, whose relative importance depends on the quantum state of reagents and products and is modulated by kinetic energy E available for reagents and/or by interatomic distance R mainly probed during the collision events
As we have extensively presented in detail in our general treatment for stereo-dynamics of state-to-state CHEMI15, it is important to point out that overlap effects with the continuum wave function of emitted electrons are here indirectly enclosed in the pre-exponential factor and this allows to better explicit the couplings between discrete quantum states which are more effective for the electronic rearrangements within the collision c omplex[15]
Summary
This paper reports on the collision dynamics of N2 with metastable Ne* promoting chemiionizations, prototype of barrier-less oxidation reactions of great interest for fundamental and applied research. Chemiionization reactions (CHEMI), known as Penning and autoionizations processes, are triggered by collisions of A * species, electronically excited in highly energetic metastable states (usually H e* and Ne* atoms which are prototype of open-shell species), with other atoms/molecules M 6,7. In most cases, they form Penning ions M+ and/or associate ions AM+ plus electrons even if ionization rearrangements and fragmentation of M+ can occur in CHEMI involving m olecules[7]. Elementary processes have been described in terms of confinement and/or transition between Hund’s cases of rotating diatoms, formed by the interacting systems during each collision e vent[17], and the selectivity of all state-to-state reaction channels has been properly identified[16]
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