DYNAMICS OF DIPOLE OF FINITE SIZE IN FIELD OF TWO DIPOLES

摘要

Dipole approximation is often used in chemistry, physics, and biophysics for systems of molecules with internal distances of the order or less than the size of the molecules. Applicability of the approximation in electrostatic interactions of closely situated extended objects is investigated. Dynamics of a dipole of finite size oscillating in the field of two identical, immobile, closely situated dipoles is examined. The characteristic quantity for the system is ε - the ratio of the length of the dipole to the distance between dipoles. There exists the critical value ε~*≈ 0.6055 independent of the magnitude of the dipole moment. For ε < ε~* the potential becomes the dipole potential. For ε > ε~* the potential differs from the dipole potential. The discrepancy increases for ε → 1. In the vicinities of equilibrium points for the dipole potential there appear some new critical points, discussed in the paper. They change completely the behavior of the system slightly moved out of the equilibrium. In the flat ε > ε~* case equations are solved numerically.