Frequency dependence of EPR signal intensity, 248 MHz to 1.4 GHz

The electron paramagnetic resonance pulsed free induction decay (FID) of a degassed solution of a triaryl methyl radical, methyl tris(8-carboxy-2,2,6,6-tetramethyl(-d3)-benzo[1,2-d:4,5-d']bis(1,3)dithiol-4-yl) tripotassium salt, 0.2 mM in H2O, was measured at VHF (247.5 MHz) and L-band (1.40 GHz). The calculated and observed FID signal amplitudes (in millivolts) agreed within 1 and 6%, and the ratio of the normalized FID signals at the two frequencies agreed within 5%. The FID decay time constant was 2.7 micros at both frequencies.