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A study of finite-size and non-perturbative effects on the van der Waals and the Casimir-Polder forces
KTH, School of Industrial Engineering and Management (ITM).ORCID iD: 0000-0002-5249-0211
2016 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

This licentiate thesis addresses two important aspects of the van der Waals and the Casimir-Polder ground-state and excited-state (resonance) interactions between two atoms or molecules. The first is the finite-size effect and the second is the non-perturbative effect. Going beyond the usual assumption of atoms and molecules as point particles and adopting a description of finite size, the divergence inherent in such interaction energies in the limit of zero separation distance between the two interacting atoms or molecules is removed. The attainment of finite interaction energy at such close separation distance facilitates the estimation of van der Waals force contribution to the binding energy of the molecules, and towards surfaces. This is particularly important for noble atoms. We investigate in detail for a pair of helium (He) atoms and krypton (Kr) atoms, and for a pair of methane (CH4) molecules considering its environmental importance. The application of finite size further leads to finite self energies of the atoms. The expression of the interaction energy, as is discussed in detail in this thesis, typically contains a logarithmic factor of the form ln(1-x). Formerly, in evaluating the interaction energies, this factor is customarily series-expanded and truncated in the leading order with certain assumptions. This thesis explores the effect of using the full expression, which we refer to as the non-perturbative (or, the non-expanded) theory, analytically wherever possible as well as numerically. The combined application of the finite-size theory and the non-perturbative theory results in as much as 100% correction in the self energy of atoms in vacuum. This may give rise to significant physical consequences, for example, in the permeabilities of atoms across dielectric membranes. The non-perturbative theory, in addition, exhibits interesting behaviour in the retarded resonance interaction.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2016. , 58 p.
Keyword [en]
finite-size effects, non-perturbative theory, van der Waals and Casimir Polder forces
National Category
Physical Sciences
Research subject
Materials Science and Engineering
Identifiers
URN: urn:nbn:se:kth:diva-186225ISBN: 978-91-7595-981-8 (print)OAI: oai:DiVA.org:kth-186225DiVA: diva2:926289
Presentation
2016-05-23, N111 Kuben, MSE ITM, Brinellvägen 23, KTH-Campus, Stockholm, 13:15 (English)
Opponent
Supervisors
Note

QC 20160509

Available from: 2016-05-09 Created: 2016-05-05 Last updated: 2016-05-09Bibliographically approved
List of papers
1. Finite-size-dependent dispersion potentials between atoms and ions dissolved in water
Open this publication in new window or tab >>Finite-size-dependent dispersion potentials between atoms and ions dissolved in water
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2014 (English)In: Europhysics letters, ISSN 0295-5075, E-ISSN 1286-4854, Vol. 106, no 5, 53002- p.Article in journal (Refereed) Published
Abstract [en]

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.

Keyword
Correlated Molecular Calculations, Gaussian-Basis Sets, Energy
National Category
Other Physics Topics
Identifiers
urn:nbn:se:kth:diva-149225 (URN)10.1209/0295-5075/106/53002 (DOI)000339151800008 ()2-s2.0-84902171506 (Scopus ID)
Funder
Swedish Research Council, C0485101
Note

QC 20140818

Available from: 2014-08-18 Created: 2014-08-18 Last updated: 2017-12-05Bibliographically approved
2. Intermolecular Casimir-Polder forces in water and near surfaces
Open this publication in new window or tab >>Intermolecular Casimir-Polder forces in water and near surfaces
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2014 (English)In: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics, ISSN 1539-3755, E-ISSN 1550-2376, Vol. 90, no 3, 032122- p.Article in journal (Refereed) Published
Abstract [en]

The Casimir-Polder force is an important long-range interaction involved in adsorption and desorption of molecules in fluids. We explore Casimir-Polder interactions between methane molecules in water, and between a molecule in water near SiO2 and hexane surfaces. Inclusion of the finite molecular size in the expression for the Casimir-Polder energy leads to estimates of the dispersion contribution to the binding energies between molecules and between one molecule and a planar surface.

Keyword
Casimir-Polder force, Near surfaces
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-154762 (URN)10.1103/PhysRevE.90.032122 (DOI)000342562600002 ()2-s2.0-84907279845 (Scopus ID)
Funder
Swedish Research Council, 90499401
Note

QC 20141104

Available from: 2014-11-04 Created: 2014-10-27 Last updated: 2017-12-05Bibliographically approved
3. Non-perturbative theory of dispersion interactions
Open this publication in new window or tab >>Non-perturbative theory of dispersion interactions
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2015 (English)In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. 90, no 3, 035405Article in journal (Refereed) Published
Abstract [en]

Some open questions exist with fluctuation-induced forces between extended dipoles. Conventional intuition derives from large-separation perturbative approximations to dispersion force theory. Here, we present a full non-perturbative theory. In addition, we discuss how one can take into account finite dipole size corrections. It is of fundamental value to investigate the limits of validity of the perturbative dispersion force theory.

Keyword
fluctuation forces, non-perturbative theory, van der Waals interactions
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-163995 (URN)10.1088/0031-8949/90/3/035405 (DOI)000350866700023 ()2-s2.0-84924301472 (Scopus ID)
Funder
Swedish Research Council, C0485101
Note

QC 20150507

Available from: 2015-05-07 Created: 2015-04-13 Last updated: 2017-12-04Bibliographically approved
4. Nonperturbative theory for the dispersion self-energy of atoms
Open this publication in new window or tab >>Nonperturbative theory for the dispersion self-energy of atoms
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2014 (English)In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 90, no 5, 054502- p.Article in journal (Refereed) Published
Abstract [en]

We go beyond the approximate series expansions used in the dispersion theory of finite-size atoms. We demonstrate that a correct, and nonperturbative, theory dramatically alters the dispersion self-energies of atoms. The nonperturbed theory gives as much as 100% corrections compared to the traditional series-expanded theory for the smaller noble gas atoms.

National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:kth:diva-158403 (URN)10.1103/PhysRevA.90.054502 (DOI)000345414100014 ()2-s2.0-84910601102 (Scopus ID)
Note

QC 20150109

Available from: 2015-01-09 Created: 2015-01-07 Last updated: 2017-12-05Bibliographically approved

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Priyadarshini, Thiyam

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