Reactive collisions in gases of energetic interest

This thesis devoted to the study of reactive collisions in gases of energetic interest concerns two aspects. Firstly, a Multichannel-Quantum-Defect-Theory - type approach [Giusti 1980, Nakashima 1987] is used in the treatment of the dissociative recombination (DR), vibrational excitation (VE), and vibrational de-excitation (VdE) of BeH⁺ ion and its isotopomers in their four lowest vibrational states (X¹Σ⁺, v_i⁺ = 0, 1, 2, 3). The molecular structure data previously computed [Roos 2009] have been employed in the calculations of cross sections and rate coefficients of DR, VE and VdE including three electronic symmetries of BeH (²Π, ²Σ⁺ and ²Δ). The vibrational dependence [Niyonzima 2013] and the isotopic effects in these collisional processes are highlighted - Figure (V.7) - in order to be used in the modeling of the edge fusion plasma [Celiberto 2012]. Satisfactory agreement with results computed with the wave packet method [Roos 2009] is reached at intermediate energies [Niyonzima 2013]. Thereby, this part of the thesis work extends the previous study of [Roos 2009]. The MQDT-based approach, able to fully account for the temporary captures of electrons in Rydberg bound states, as well as the vibronic coupling between ionization channels, provides the first results (reliable) at low energies [Niyonzima 2013]. Lastly, an approximate analytical formulation of DR, VE and VdE cross section for the prediction and interpretation of results of numerical calculations has been provided. This formulation is useful in the understanding of different intramolecular interactions and explains the sensibility of rate coefficients with respect to dominant interactions. (author)