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

¹ Department of Materials Science and Engineering, Royal Institute of Technology SE-100 44 Stockholm, Sweden, EU
² Centre for Materials Science and Nanotechnology, University of Oslo - P. O. Box 1048 Blindern, NO-0316 Oslo, Norway
³ Department of Energy and Process Engineering, Norwegian University of Science and Technology NO-7491 Trondheim, Norway
⁴ Department of Physics, University of Oslo - P. O. Box 1048 Blindern, NO-0316 Oslo, Norway
⁵ Department of Applied Mathematics, Australian National University - Canberra, Australia
⁶ Division of Theory and Modeling, Department of Physics, Chemistry and Biology, Linköping University SE-581 83 Linköping, Sweden, EU

Received: 17 March 2014
Accepted: 21 May 2014

Abstract

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.