Electrodynamic interaction

As previously mentioned, electrodynamic interactions, such as those arising from London forces, can also contribute to the adhesion of particles. These forces are dominated by dipole interactions and are broadly lumped into the classification known as van der Waals interactions. A more detailed description of van der Waals interactions than can be presented in this article is given in books by Israelachvili [95] and by Rimai and Quesnel [96]. 

Chemical bonding consists of electrostatic and electrodynamic interactions between valence electrons and positive ions. However, there is more than one category. In small groups of atoms (molecules), pairs of electrons may reside between pairs of ions and electrostatically attract the ions to form bonds (covalent bonding). 

Furthermore, as mentioned above the screening of the dipole field by the conduction electrons can be represented by an image dipole inside the metal. This complex of the chemisorbed molecule and its image has a vibration frequency different from that of the free molecule. The electrodynamic interaction between a dipole and its image has been discussed in many works. The theoretical problem is that the calculated frequency shift is extremely sensitive to the position of the image plane (Fig. 3a). One can with reasonable parameter values obtain a downward frequency shift of the order of 5-50 cm S but the latest work indicates that the shift due to this interaction is rather small. 

The electrodynamic interaction potential acting between a diatomic molecule and an electron outside a molecule can be written as... 

The energy operator considered above is an approximation, in which only the lowest terms of the correction for the retardation of the interaction are taken into account. More general is the formal quantum-electrodynamical interaction energy operator in the approximation of the exchange of one virtual photon [58]... 

Written as the sum over the products, -AAmAfim, electrodynamic interactions show a kind of specificity. They prefer the interaction of like, resonating materials compared with the interaction of unlike species. This specificity, though, occurs as a difference between possible combinations of interactions If A and B are made of different substances, then the sum of A-A and B-B interactions is always less than two interactions A-B. Term by term in the sum, there is the inequality [from the inequality of geometric and arithmetic means that says ab < (a2 + b2)/2] ... 

Note Spheres From Eq. 41, V. A. Parsegian and G. H. Weiss, "Electrodynamic interaction between curved parallel surfaces,"J. Chem. Phys. 60, 5080-5085 (1974) ... 

N is the number of rods per unit area, and Nna2 is the volume fraction of rods in the array. Only when Nna2A electric field that is distorted by its neighbors. In the same way, the electric fields created and received by electrodynamically interacting rods are in fact felt by many rods at the same time. 

Classically, dispersion comes up from induced-dipole—induced-dipole interactions. The fluctuations in electrodynamic interactions in the electronic density between two interacting molecules, couple and reduce the overall electrostatic energy. This is in opposition to the polarization from an electrostatic description. There is plenty of controversy regarding the composition of the energies obtained by several DFT functionals. It is claimed... 

A further term, which has no analogue in hydrogen, arises in the fine structure of positronium. This comes from the possibility of virtual annihilation and re-creation of the electron-positron pair. A virtual process is one in which energy is not conserved. Real annihilation limits the lifetimes of the bound states and broadens the energy levels (section 12.6). Virtual annihilation and re-creation shift the levels. It is essentially a quantum-electrodynamic interaction. The energy operator for the double process of annihilation and re-creation is different from zero only if the particles coincide, and have their spins parallel. There exists, therefore, in the triplet states, a term proportional to y 2(0). It is important only in 3S1 states, and is of the same order of magnitude as the Fermi spin-spin interaction. Humbach [65] has given an interpretation of this annihi-... 

QED provides a framework for describing the role of the negative energy states in the Dirac theory and the divergences which arise in studies of electrodynamic interactions.83-85 In Section 2.3 it will be shown how the use of the algebraic approximation to generate a discrete representation of the Dirac spectrum has opened the way for the transcription of the rules of QED into practical algorithms for the study of many-electron systems. 

As a second example for modifications of the quantum electrodynamical interaction between matter and the radiation field originating from controlled mode engineering in the following we discuss the spontaneous decay of a two-level system, such as an ion [24], in a half-open cavity with a... 

Pinchuk AO, Kalsin AM, Kowaiczyk B, Schatz GC, Grzybowski BA (2007) Modeling of electrodynamic interactions between metal nanoparticles aggregated by electrostatic interactions into closely-packed clusters. J Phys Chem C 111(32) 11816-11822. doi 10.1021/jp073403v... 

Cencek, W, Komasa, J., Przybytek, M., Mehl, J. B., Jeziorski, B., and Szalewicz, K., Effects of Aadiabatic, Relativistic, and Quantum Electrodynamics Interactions in Helium Dimer on Thermophysical Properties of Helium,/. Chem. Phys., to be submitted (2011). 

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