EPR investigation of the methyl radical,the hydrogen atom and carbon oxide radicals in Maxixe-type beryl |
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Authors: | Lars Olov Andersson |
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Affiliation: | (1) Brunnenweid 49, CH-5643 Sins, Switzerland |
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Abstract: | The EPR spectra of Maxixe-type beryl contain a large number of overlapping signals. The angular dependence of the 1:3:3:1 signal typical for the CH3 radical shows that this radical is located at the center of the channel cavity with its symmetry axis parallel to the crystal c-axis and is rotating around this axis. Its EPR spectrum is axially symmetric with g // = 2.00263, g ⊥ = 2.00249 and A// = 2.288 mT, A⊥ = 2.256 mT. These anisotropies have the opposite signs of those found for surface-adsorbed methyl radicals. Hydrogen atoms are located at position 2a at the center of the beryl cavity and the EPR parameters of the narrow doublet signal are A 0 = 1,407 MHz and g = 2.00230. Another doublet signal, which is broader and has axial symmetry with g // = 2.00265, g ⊥ = 2.00625 and A// = 0.895 mT, A⊥ = 0.885 mT, could come from a HCO3 radical. One narrow and easily saturated signal with g // = 2.00227 and g ⊥ = 2.00386 is interpreted to arise from a carbon monoxide radical in the beryl channel, oriented with its axis parallel to the crystal c-axis. Additional weak doublet lines, which have similar g values as the carbon monoxide radical, are created by nearby hydrogens. A powder spectrum with g // = 2.0017 and g ⊥ = 2.0004 appears upon UV irradiation of the single crystal and is easily saturated. This spectrum is interpreted to arise from a carbon dioxide radical, which rotates around its symmetry axis. |
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Keywords: | Maxixe-type beryl EPR Hydrogen atom HCO3 radical Methyl radical Carbon monoxide radical Carbon dioxide radical |
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