Transport and relaxation cross-sections for pure gases of linear molecules Original Research Article

The program calculates thermally averaged generalized cross-sections of a pure gas of molecules which can be treated as rigid rotors. The 10-dimensional integration required is performed in two stages: (i) the total energy integration using a Chebyshev interpolation scheme and an automatic integrator based on the Clenshaw-Curtis formula; (ii) the remaining 9-dimensional integration is approximated by a Monte Carlo sum over N classical trajectories. Each trajectory is calculated by numerical integration of Hamiltonʹs equations in the radial momentum and distance and the action-angle variables of a two rigid rotor system, exploiting conservation of total angular momentum.