High-Field (3.4 T) ENDOR Investigation of Asphaltenes in Native Oil and Vanadyl Complexes by Asphaltene Adsorption on Alumina Surface

Figure 5

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 [59] 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 .