Properties of methyl radical trapped in amorphous SiO2 and in natural SiO2-clathrate Melanophlogite

► CH3 is observed in irradiated amorphous SiO2 and in Melanophlogite. ► The rotational correlation time of CH3 molecules at T = 77 K is measured by EPR. ► Relevant information on the interstices in which the radical is confined is obtained. ► The comparison between amorphous SiO2 and Melanophlogite is found to be fruitful.