ESR investigations of burnt soil

Electron spin resonance (ESR) of transition metal ions (Mn2+, Fe3+), radiation induced centres and pyrolytically formed radicals was studied to distinguish between burnt and unburnt soil. A testfire place and samples from an archaeological site were analyzed. The concentration of radiation induced centres decreases and pyrolytically formed radicals appear in a thermal annealing experiment. The spectral pattern of iron and manganese resonances changes during the heating process. These signals are useful to estimate temperature and atmosphere of the heating event. Chemithermoluminescence (CTL) of the soil was studied and could reveal its thermal history, too.