Fokker-Planck equation for chemical reactions in plasmas.
Speaker: Paola Diomede (Fusion Energy, DIFFER)
Time: June 7, 2018, 10:00–11:00
Location: Differ, Alexander-zaal
In non-equilibrium plasmas, the kinetics of chemical reactions involving species with internal levels is very complex because of the high number of quantum states whose population is changing in the course of the process and must be accounted for.
Under such conditions, the application of the present state-to-state models, where any internal level is considered as an individual species, is complicated and the resulting codes are physically quite opaque, making it difficult to find the key parameters of the process. In this seminar, I will illustrate the development of numerical methods based on the reconsideration of the old-fashioned diffusion formalism, where the internal kinetics is described by a Fokker-Planck (FP) equation and the transport coefficients are determined from first principles, in the light of the present availability of computational facilities. In particular, a time dependent solution of the FP equation can be obtained using the Diffusion Monte Carlo method. The method is demonstrated using the plasma activation of CO2 through its asymmetric stretching mode as a test case: In this important application, the possibility of describing dissociation kinetics as a transport process, instead of a network of elementary processes involving discrete states, provides new guidelines towards the goal of achieving a more efficient CO2 conversion.