(color online) The electrostatic pair interaction (hollow symbols) of two like-charged particles trapped in the air–water interface as a function of the dimensionless center–center distance d with different surface distributions. The solid lines are corresponding nonlinear fits (the fit equation is given in the inset). The other parameters are as follows: particle radius m, total surface charge Q = 2000 (in units of unit electric charge), T = 300 K, h = 0, and the screening length .