Electron Spin Resonance measurement of organic radicals in petroleum source rock containing transition metal ions

The Electron Spin Resonance (ESR) spectrum with the width DeltaH = 0.5 +/- 0.02 mT at g-factor of 2.0028 +/- 0.0005 of kerogen collected at the shallo w part of a petroleum deposit has a broader peak than that collected in its deeper part (DeltaH = 0.4 +/- 0.02 mT), Two groups of samples were prepare d. One was heated at several temperatures to liberate hydrocarbons and anot her was treated with pyridine, so that the generated hydrocarbons due to he ating were removed. Narrowing of the linewidth was not caused by heating, b ut by treatment with pyridine. Molecular orbital calculation was performed to explain the septet-quartet ESR spectrum of organic radicals with g = 2.0 023 +/- 0.0005, A(1) = 0.625 +/- 0.003 mT (septet) and A(2) = 0.187 +/- 0.0 03 mT (quartet) in petroleum source rock and in heated carbonate: the prese nce of tert-butyl radical can be suitable to explain the septet-quartet spe ctrum.