Thermal Conductivity of a Gas with Rotational States

Abstract

When degenerate internal states are present, the most convenient description of the average one‐particle state is by means of a Wigner distribution function‐density matrix which is a Wigner distribution function for translational motion and a density matrix in internal states. This matrix is assumed to be diagonal in energy but may in general be nondiagonal in degenerate states. The Boltzmann equation appropriate for this quantity is solved by the Chapman—Enskog method to obtain an expression for the thermal conductivity in terms of generalized quantum‐mechanical cross sections.