Viscosity of high-temperature iodine

The viscosity coefficient of iodine in the temperature range 500<=T<=3000 K is calculated. Because of the low dissociation energy of the I₂ molecules, the dissociation degree of the gas increases quickly with temperature, and I+I₂ and I+I collisions must be taken into account in calculations of viscosity at temperatures greater than 1000°. Several possible channels for atom-atom interaction are considered, and the resulting collision integrals are averaged over all the important channels. It is also shown that the rigid-sphere model is inaccurate in predictions of the viscosity. The approach of the present work is general and can be used for other diatomic gases with arbitrary dissociation degree.