Mitchell, D.G.; Tseitlin, M.; Quine, R.W.; Meyer, V.; Newton, M.E.; Schnegg, A.; George, B.; Eaton, S.S.; Eaton, G.R.: X-band rapid-scan EPR of samples with long electron spin relaxation times: a comparison of continuous wave, pulse and rapid-scan EPR. Molecular Physics 111 (2013), p. 2664-2673
10.1080/00268976.2013.792959

Abstract:
X-band room temperature spectra obtained by rapid-scan, continuous wave, field-swept echo-detected and Fourier transform electron paramagnetic resonance (FTEPR) were compared for three samples with long electron spin relaxation times: amorphous hydrogenated silicon (T1 = 11 μs, T2 = 3.3 μs), 0.2% N@C60 solid (T1 = 120–160 μs, T2 = 2.8 μs) and neutral single substitutional nitrogen centres (NS0) in diamonds (T1 = 2300 μs, T2 = 230 μs). For each technique, experimental parameters were selected to give less than 2% broadening of the lineshape. For the same data acquisition times, the signal-to- noise for the rapid-scan spectra was one-to-two orders of magnitude better than for continuous wave or field-swept echo-detected spectra. For amorphous hydrogenated silicon, T2∗ (∼ 10 ns) is too short to perform FTEPR. For 0.2% N@C60, the signal-to-noise ratio for rapid scan is about five times better than for FTEPR. For NS0 the signal-to-noise ratio is similar for rapid scan and FTEPR.