Collision Integrals and Orbiting Analysis for Polar Species Using the Stockmayer Potential

Polar species appear in several planetary entry problems in both the shock-heated gas and its interaction with the ablative heat shield or other active cooling systems. Typically, the contributions of polar species to plasma transport properties are evaluated using spherical phenomenological potential functions or, more recently, with ab initio computations. Limited consideration has been given to the use of nonspherical potential functions for polar species. The Stockmayer potential is a Lennard–Jones potential function modified to account for polar interactions. In this paper, the Stockmayer potential is used to compute collision integrals for NO, CN, CO, and CH. Additionally, a methodology applicable to potential functions similar in form to the Lennard–Jones potential is developed to determine scaling laws that describe the asymptotic behavior of the orbiting boundary at low energies. The use of the nonspherical Stockmayer potential function preserves agreement with the Lennard–Jones potential at moderate to high temperatures (above 5000 K) when potential parameters are selected consistently. This indicates that the polarity of species at these temperatures does not strongly impact transport properties.