Therefore, the fringe length of par

Therefore, the fringe length of particles at 40 mm HAB is the shortest. The mean fringe length data are presented in Table 2. FL shows a trend of decreasing first and then increasing, and the minimum value is at 40 mm HAB. From 35 mm to 40 mm HAB, during the growth of soot particles, due to overlap between electron orbitals in the carbon layers, the repulsion between adjacent carbon layers is produced [16]. In order to achieve the minimum energy stable state, the fringe length of the carbon layers is reduced [38]. As the particles approaching the flame tip from 40mm HAB, the microcrystalline carbon layers on the surface of soot particles are oxidized due to the activity of their structure, which results in the increase of fringe length in the end.