The Journal of Chemical Physics · 1965 · 48 citations · 4 references
Natural SciencesChemistryPhysicsCrystal StructureMolecular PhysicsSpectroscopyElectron Paramagnetic ResonanceElectron Spin Resonance SpectroscopyHyperfine StructureMagnetic Resonance SpectroscopyMolecular SymmetrySpectroscopy Of BiomoleculesBonding OrbitalsHyperfine Structure AnalysisHyperfine Structure ConstantsHyperfine Structure ExcitationHyperfine Structure MeasurementsResonanceSingle Crystal AnalysisSpin-lattice Relaxation Effects
An electron paramagnetic resonance study has been made on a single crystal of L-cysteine hydrochloride irradiated with a 1.5-MeV electron beam at 77°K. The hyperfine structure of the main resonance pattern was found to be an almost isotropic double doublet, whereas the g factor was found to be highly anisotropic but axially symmetrical, the principal values being 2.29, 1.99, and 1.99. The main resonance has been attributed to the free radical HOOC–CH–CH2–S. – NH3Clwith the unpaired electron occupying one of the two nearly degenerate orbitals of the sulfur atom. A remarkable broadening of the resonance spectrum was observed at elevated temperatures, and evidence is given that this broadening is due to a short spin—lattice relaxation time due to a large spin—orbit coupling in this free radical.
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