Gas-phase EPR of polyatomic radicals

EPR spectra are reported from three nitroxides, five carbon-centred radicals and one oxyaminyl radical in medium- and low-pressure organic gases. The linewidths semi-quantitatively agree with theoretical predictions, i.e. increase with the g-anisotropy of the radical and decrease with increasing gas pressure and size and mass of the radical. In many cases linewidths were small enough for gas-phase conditions to give well-resolved spectra. Thus for the tert-butyl radical in ethanol at 600 K, the linewidth increased linearly with P−1 from 1 to only 4 G between 60 and 7 bar.