ELECTROSTATIC FREE-ENERGY OF IONS OF FINITE-SIZE CLOSE TO FLAT INTERFACES BETWEEN DIELECTRIC MEDIA

The electrostatic free energy profile for transfer of an ion between dielectric phases separated by a flat interface was analytically calculated. The calculated free energy accounts for the ion's finite size and for its interaction with the image charge. As the ion crosses the interface its free energy does not exhibit the singularity peculiar to point-charge models, and can be used to describe the capacitance of the electric double layer found at interfaces between immiscible liquids during partial ion transfer.