Rotational Collision Numbers of N2, O2, CO, and CO2 from Thermal Transpiration Measurements

Thermal transpiration results which were determined at an (assumed) characteristic temperature of 504°K are reported for all of the noble gases and for N2, O2, CO, and CO2. The helium data are found to be anomalous when viewed in terms of the dusty-gas model for thermal transpiration. Application of the model in the zeroth differential approximation yields the following rotational collision numbers for the polyatomic molecules: N2, 6.0; O2, 2.2; CO, 1.3; CO2, 1.9.