The influence of magnetic fields on the gaseous thermal conductivity of N2 and CO



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In a dilute gas of molecules containing rotational states a temperature gradient produces a polarization of the molecular angular momenta. Its influence on the thermal conductivity of the gas can be observed by partially destroying this polarization with the application of an external magnetic field. An apparatus for measuring the influence of magnetic fields on the thermal conductivity of gases over the 77°K to 300°K temperature range is described. Senftleben-Beenakker thermal conductivity measurements on the average of the perpendicular and parallel effects for N[subscript 2] at 300°K is presented. Moreover, both, the average and perpendicular effect measurements on N[subscript 2] and CO at 79°K are presented. The results for N[subscript 2] at 300°K confirm earlier similar measurements and establish the reliability of the experimental apparatus. The low temperature results for N2 and CO, taken for the first time, show a 25-35% decrease in the saturation values. Experimental collision cross sections calculated from this data are approximately a factor of two larger than room temperature results. They exhibit approximately the same temperature dependence as those calculated from elastic collision theory. Orientation effects, determined from the low temperature results, agree with previous measurements taken at 300°K. This suggests that the relative contribution of various terms in the theoretical expansion for the nonequilibrium distribution function is temperature independent.