NUCLEAR-SPIN CONVERSION IN CH3F AT ELEVATED-TEMPERATURES

Experimental data on the temperature dependence of the ortho-para nucl ear spin conversion rate of gaseous CH3F are presented. In the range 3 00-750 K, the (CH3F)-C-12 conversion rate increases by one order of ma gnitude. By contrast, the conversion rate for (CH3F)-C-13 decreases wi th increasing temperature (for T<600 K). These results are in qualitat ive agreement with a theoretical model based on mixing of states due t o intramolecular spin-spin interactions between the-molecular nuclei. Above 600 K, the rate in (CH3F)-C-13 starts to increase again, indicat ing a possible additional mechanism for the conversion.