Electron spin echo at S-band: Nuclear modulations and decay in C60 powder

At S-band (≈ 3 GHz) the modulation amplitude of the Electron Spin Echo patterns is increased with respect to the amplitude at X-band: as a consequence, it is possible to reveal the presence of nuclei not detectable at X-band. In this paper the results obtained by running ESE experiments at S-band on a C₆₀ powder sample containing radicals are shown and discussed. The two- and three-pulse Electron Spin Echo patterns exhibit both¹³C modulation and proton modulation not detected at X-band. The experimental data are quantitatively analyzed by simulating the time-domain patterns and their Fourier transforms. It results that a noticeable amount of proton nuclei surrounds the intrinsic paramagnetic centers. On the basis of the analysis, a possible explanation of their existence is given.