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Register a new userComprehensive Quantum Framework for Describing Retarded and Non-Retarded Molecular Interactions in External Electric Fields
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We employ various quantum-mechanical approaches for studying the impact of electric fields on both nonretarded and retarded noncovalent interactions between atoms or molecules. To this end, we apply perturbative and non-perturbative methods within the frameworks of quantum mechanics (QM) as well as quantum electrodynamics (QED). In addition, to provide a transparent physical picture of the different types of resulting interactions, we employ a stochastic electrodynamic approach based on the zero-point fluctuating field. Atomic response properties are described via harmonic Drude oscillators - an efficient model system that permits an analytical solution and has been convincingly shown to yield accurate results when modeling non-retarded intermolecular interactions. The obtained intermolecular energy contributions are classified as field-induced (FI) electrostatics, FI polarization, and dispersion interactions. The interplay between these three types of interactions enables the manipulation of molecular dimer conformations by applying transversal or longitudinal electric fields along the intermolecular axis. Our framework combining four complementary theoretical approaches paves the way toward a systematic description and improved understanding of molecular interactions when molecules are subject to both external and vacuum fields.
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Retarded electromagnetic potentials are derived from Maxwells equations and the Lorenz condition. The difference found between these potentials and the conventional Li{e}nard-Wiechert ones is explained by neglect, for the latter, of the motion-dependence of the effective charge density. The corresponding retarded fields of a point-like charge in arbitary motion are compared with those given by the formulae of Heaviside, Feynman, Jefimenko and other authors. The fields of an accelerated charge given by the Feynman are the same as those derived from the Li{e}nard-Wiechert potentials but not those given by the Jefimenko formulae. A mathematical error concerning partial space and time derivatives in the derivation of the Jefimenko equations is pointed out.
In Grossu et al. (2012) we presented a Chaos Many-Body Engine (CMBE) toy-model for chaos analysis of relativistic nuclear collisions at 4.5 A GeV/c (the SKM 200 collaboration) which was later extended to Cu + Cu collisions at the maximum BNL energy. Inspired by existing quark billiards, the main goal of this work was extending CMBE to partons. Thus, we first implemented a confinement algorithm founded on some intuitive assumptions: 1) the system can be decomposed into a set of two or three-body quark white clusters; 2) the bi-particle force is limited to the domain of each cluster; 3) the physical solution conforms to the minimum potential energy requirement. Color conservation was also treated as part of the reactions logic module. As an example of use, we proposed a toy-model for p + p collisions at sqrt(s)=10 GeV and we compared it with HIJING. Another direction of interest was related to retarded interactions. Following this purpose, we implemented an Euler retarded algorithm and we tested it on a simple two-body system with attractive inverse-square-law force. First results suggest that retarded interactions may contribute to the Virial theorem anomalies (dark matter) encountered for gravitational systems (e.g. clusters of galaxies). On the other hand, the time reverse functionality implemented in CMBE v03 could be used together with retardation for analyzing the Loschmidt paradox. Regarding the application design, it is important to mention the code was refactored to SOLID. In this context, we have also written more than one hundred unit and integration tests, which represent an important indicator of application logic validity.
We study the interaction between two neutral atoms or molecules subject to a uniform static electric field, using quantum mechanics (QM) and quantum electrodynamics (QED) applied to coupled harmonic Drude oscillators. Our focus is to understand the interplay between dispersion interactions and field-induced electrostatics and polarization in both retarded and non-retarded regimes. We present an exact solution for two coupled oscillators using QM and Rayleigh-Schrodinger perturbation theory, demonstrating that the external field controls the strength of different intermolecular interactions and relative orientations of the molecules. In the retarded regime described by QED and rationalized by stochastic electrodynamics, our analysis shows that field-induced electrostatics and polarization terms remain unchanged (in isotropic and homogeneous vacuum) compared to the non-retarded QM description, in contrast to a recent work. Our framework combining four complementary theoretical approaches paves the way to a systematic description and enhanced understanding of molecular interactions under the combined action of external and vacuum fields.
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Cecilia Noguez
, Carlos E. Roman-Velazquez
, Raul Esquivel-Sirvent andn Carlos Villarreal
2003
We calculate exactly the Casimir force or dispersive force, in the non-retarded limit, between a spherical nanoparticle and a substrate beyond the Londons or dipolar approximation. We find that the force is a non-monotonic function of the distance between the sphere and the substrate, such that, it is enhanced by several orders of magnitude as the sphere approaches the substrate. Our results do not agree with previous predictions like the Proximity theorem approach.
An approach is outline to constructing an optical potential that includes the effects of antisymmetry and target recoil. it is based on the retarded Greens function, which could make it a better starting point for applications to direct nuclear reactions, particularly when extended to coupled channels. Its form retains a simple connection to folding potentials, even in the presence of three-body forces.
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