University of Bari, Italy

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University Bari, Italy
M. Capitelli
Semi-classical impact parameter method is used to calculate vibrationally-resolved cross section for excitation and dissociation for spin–allowed transitions. Some of these calculated data are already available on the ALADDIN web page. The quasi-classical trajectory approximation has been used to calculate vibrational translational relaxation and dissociation for H, H2, and isotopic variants. Calculations of atom-molecule gas surface interaction have been carried out, specifically for atomic hydrogen or deuterium on copper or graphite. Resonant charge transfer of electronically excited states in atom-ion, highly-excited atoms can be calculated.

State-to-State Kinetics of Molecular and Atomic Hydrogen Plasmas[1]

The activity in the Plasma Chemistry group in Bari is focused on state-to-state kinetic modeling of systems of interest for technological applications ranging from fusion (negative ion sources) to aerospace. Concerning the tools for the derivation of information on the dynamics of elementary processes, recent results include:

  • the implementation of a simplified theoretical approach, the similarity function, for the calculation of cross sections for electron-impact induced vibronic excitation in diatomic molecules with resolution on internal degrees of freedom, giving results that compare well both to theory and experiments in the case of e-H2 excitation and avoiding the high computational load of more accurate methods;
  • new implementation of the code for resonant processes in electron-molecule collisions (resonant vibrational excitation and dissociative attachment) for the investigation of isotopic effects, considering the different role for the three relevant resonances in e-H2 scattering;
  • the inclusion of non-adiabatic effects, due to coupling among different potential energy surface, in the QCT (quasi-classical trajectory) code for the treatment of H++H2 system, representing a new frontier including quantum effects in the dynamics;
  • the implementation of a numerical tool based on the Downhill Simplex Method for the deconvolution of rate coefficients to cross sections, validated in the case of well-known systems as H+H2;
  • the code for the semi-classical treatment of heterogeneous processes of atom recombination at surfaces has been used for the investigation of isotopic effect in the Eley-Ridael mechanism of deuterium on graphite.

For the simulation of plasmo-chemical systems, two existing codes have been coupled, the collisional-radiative model, for an atomic hydrogen plasma under shock-wave condition, and the code for calculation of synthetic hydrogen spectrum, deriving plasma optical properties, i.e. emissivity and absorption coefficient. The role of non-equilibrium in internal distribution in affecting the spectrum is investigated in different position of the shock.

Finally thermodynamics and transport of plasmas have been studied. In particular, thermodynamic properties have been calculated in the frame of a novel approach that reduces complex systems of levels to an equivalent system of two-three levels by means of grouping. Moreover the quantum problem of levels for hydrogen atom confined in a spherical box has been investigated in the frame of solution of divergence of internal partition function.

Modules for transport coefficients calculation have been implemented including the effects of different choices of cut-off criterion and of electronically excited states (EES) in the mixture.


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