High-Field (3.4 T) ENDOR Investigation of Asphaltenes in Native Oil and Vanadyl Complexes by Asphaltene Adsorption on Alumina Surface
The energy levels (the top panel for the magnetic field directed along “out-of-plane” while the bottom one for the magnetic field “in-plane,” see Figure 3) and the corresponding absorption EPR spectrum (central panel) for VO2+ complex calculated for the microwave frequency ,,,, and . Particular contributions from every EPR transition are color-marked. Calculations are done in EasySpin package for MatLab  in the assumption that the main axes of and tensors coincide. The arrows mark the values of the magnetic field equivalent to the values of and . The values of external magnetic field that correspond to the EPR transitions with are denoted as and .