High Temperature Transport Properties of Dilute Nitrogen Atoms

Abstract

Calculations of the transport coefficients viscosity and thermal conductivity and the diffusion collision cross section of nitrogen atoms have been carried out as a function of temperature. The dilute gas transport properties of nitrogen atoms depend only on the interactions between two nitrogen atoms along various electronic potential energy curves. The results presented here include contributions from 16 potential energy curves, four of which dissociate to two ground-state nitrogen atoms with the others also dissociating to two nitrogen atoms, at least one of which is in an excited electronic state. Thirteen of the potential energy curves are represented by the Hulburt–Hirschfeleder potential which is the best general purpose atom–atom potential. This potential depends only on the experimental spectroscopic constants and not on any adjustable parameters. Where spectroscopic constants are unavailable, fits of the Hulburt–Hirschfelder potential to ab initio quantum mechanical results are used for two states and a fit of the Morse potential is used for the other state. The results presented here should be especially useful under conditions where nitrogen atoms are at high temperatures, such as during Space Shuttle re-entry.