Fig. 3
Interactions between pairwise particles. a A combined statistical distribution of all surface separation distance during the process of approaching in the observed OA events by 21 particle pairs. b Interaction potential of particle pairs as a function of their separation distance. The values for the potential (red dots) are extracted from statistics in (a) using Boltzmann distribution: \(P(D) = C\exp ( - U(D)/k_{\mathrm{B}}T)\), where U(D) is the combined potential energy resulting from the steric-hydration repulsive force and the van der Waals attractive force. The fitted potential and the corresponding force (\(F(D) = - {\mathop{\rm d}\nolimits} U(D)/{\mathop{\rm d}\nolimits} D\)) are shown by solid blue and dashed magenta curves, respectively. c Separation distance between 12 particle pairs during their approaching vs. relative time (while assuming that contact occurs at 0 s). Solid line is the average distance for these particle pairs. d Schematic illumination of the whole OA process
