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Finite-size–dependent dispersion potentials between atoms and ions dissolved in water

P. Thiyam, M. Boström, C. Persson, D. F. Parsons, I. Brevik, and Bo E. Sernelius

Europhysics Leters (EPL), 106 (2014) 53002       doi: 10.1209/0295-5075/106/53002

A non-expanded theory is used for dispersion potentials between atoms and ions dissolved in a medium. The first-order dispersion interaction between two atoms in an excited state must account for the fact that the two atoms are coupled via the electromagnetic field and must include effects from background media, retardation and finite size. We show that

finite-size corrections when two particles are close change the dispersion interactions in water by several orders of magnitude. We consider as four illustrative examples helium atoms, krypton atoms, phosphate ions, and iodide ions. We demonstrate that, due to large cancellation effects,

retardation dominates the interaction for helium atom pairs in an isotropic excited state down to the very small atom-atom separations where finite-size corrections are also important.

Retarded Casimir-Polder interaction between pairs of iodide ions (I)  and pairs of phosphate ions (PO43− ) dissolved in water. The curves compare theory with and without finite size.   The sizes for iodide and phosphate ions are a = 2.12Å and a = 2.40Å, respectively

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Last updated: 06/13/14