The Role of Inelastic Rotational and Vibrational Collisions on Transport Coefficients
The Wang Chang-Uhlenbeck theory of rate coefficients for relaxation and transport (thermal conductivity, viscosity, self-diffusion) for molecular gases are considered. Firstly, the formal results of the theory are discussed for correctness in comparison with the proper theory of transport coefficients. Then some earlier published calculational results for a nitrogen gas using a Monte Carlo treatment of the bimolecular collisions following classical dynamics and also semiclassical dynamics are considered particularly for the meaning of the contribution from the vibrational degrees of freedom to the transport coefficients at high temperatures. These calculations were partly carried out for rotationally, non-vibrating molecules and partly for fully coupled rotational and vibrational degrees of freedom. From the collisional treatment one realised that the first-order treatment of the Wang Chang-Uhlenbeck theory is useful for calculations of transport coefficients for temperatures where the rigid rotor model is appropriate. The results at higher temperatures indicate that inclusion of a quantum mechanical treatment of vibration or eventually higher order terms in the Wang Chang-Uhlenbeck theory is necessary.
KeywordsTransport Coefficient Excitation Transfer Collision Integral Vibrational Degree Rotational Relaxation
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