A post-collision internal energy model for O(3P) + SO2(X, 1A 1) in DSMC based on Molecular Dynamics computations

Neal Parsons, Deborah A. Levin

Research output: Contribution to journalArticlepeer-review


A model is developed for determining molecular internal energies after O(3P) + SO2(X,1A1) collisions in the Direct Simulation Monte Carlo (DSMC) method in order to improve modeling of the hyperthermal interactions occurring in the upper atmosphere of Io. Molecular Dynamics/Quasi-Classical Trajectory (MD/QCT) studies are conducted to generate post-collision SO2 and post-dissociation SO internal energy distributions as a function of initial SO2 internal energy and relative collision velocity, which are found to be an improvement over the baseline Larsen-Borgnakke (LB) method that often predicts unphysical internal energies above the dissociation energy for non-reacting collisions and under-predicts post-dissociation SO internal energy. An approach for sampling from the MD/QCT-based internal energy distributions in DSMC is developed and DSMC simulations are then conducted for a time-dependent thermal nonequilibrium heat bath using both the MD/QCT-based distributions and the LB model. When only SO2-O collisions are considered, noticeable differences are observed for post-collisional SO2 and SO internal temperatures.

Original languageEnglish (US)
Pages (from-to)33-44
Number of pages12
JournalChemical Physics
StatePublished - Oct 31 2014
Externally publishedYes


  • Direct Simulation Monte Carlo
  • Planetary simulations
  • Post-collision energy distributions
  • Quasi-Classical Trajectories
  • Thermochemical nonequilibrium

ASJC Scopus subject areas

  • General Physics and Astronomy
  • Physical and Theoretical Chemistry


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