Long range attractive polarization

The short range repulsive part Varises from the overlap of the electronic cloud of the atom and the surface electrons while the long range attractive polarization potential V. has the asymptotic form ... 

The first microscopic theory for ionic friction in polar solvents was proposed by Wolynes, " in which the ion—solvent interactions were partitioned into short-range repulsive and long-range attractive components. The friction coefficient in the Wolynes model is simplified into the following two terms ... 

These are long-ranged attractive interactions between non-polar groups separated by water. The interactions are moderately strong (5-40 kJ/mol) and endothermic (up to around 60 °C). 

The assumption that an electron can be described as a quasi-free particle implies that the interaction between the electron and any atom in the liquid is weak. It is then necessary that the attractive potential of the nucleus experienced by the electron penetrating the atomic core and the long range core polarization potential will be balanced by the electron s increased kinetic energy in the nuclear region. This restriction implies that the pseudopotential of the atom should be small. 

Table 16.2 Long-range Attractions for Polar Molecules at 298 K...

Levitation of Cs atoms in the evanescent field has been demonstrated in Ref. [Hammes 2002], where the the optical dipole potential created by 1 W-laser has been utilized for trapping the atoms far from the surface. The exponential profile of the potential decreases at a half-wave length A/,/w,/2 250 nm. At these distances the optical field compensates for the long-range attraction induced by the electrostatic polarization and the Casimir-Polder potential... 

The long range attractive potential for a diatomic dissociation is given by V r) = r ", where n is the interaction parameter. Typically = 6 for a neutral molecule (recall the Lennard-Jones 6-12 potential). On the other hand, for an ionic dissociation into an ion and a polarizable neutral, n = 4. The Hamiltonian for such a two-body central force system can be expressed in the center of mass as a one-body problem with reduced mass p. and relative velocity v. In polar coordinates, this takes the form [(Eq. 2.15)]... 

The first attempt toward the microscopic theory of the ionic friction in polar solvents has been put forward by Wolynes with his insightful paper in which ion-solvent interactions are decomposed into a short-range repulsive and a long-range attractive parts [73]. The ionic friction coefficient (, related to the fluctuations of the random forces exerted on an ion, then splits into components arising from the correlations of the hard repulsive (H) and soft attractive (S) parts of the random force ... 

At low temperatures bulk vibrational relaxation shows evidence of the long-range attractive intermolecular forces. This is particularly so between molecules with polar bonds that also strongly absorb radiation in the near infrared. Such strong absorption indicates that the molecule can easily be distorted from its equilibrium position by the elecfrical field of the light. In a colUsion experiment such a time-dependent field can be provided by the motion of the other polar... 

There are a number of theoretical prescriptions for determining rate coefficients of exothermic ion-molecule reactions. The simplest originates from concepts developed more than a century ago by Langevin and applies to a reaction between a point ion and a spherical (non-polar) molecule [20]. The dominant long-range attractive force in this case is the ion-induced dipole interaction, which takes the form... 

A range of smface force methods have been used during the last 25 years for accmate measurements of classical DLVO forces (electrostatic doublelayer and van der Waals forces), polymer-induced forces (steric, bridging, depletion) under a range of solvency conditions, as well as short-range hy-dration/protrusion forces and long-range attractive forces between nonpolar surfaces in polar solvents. In particular, the interferometric stuface force... 

The van der Waals forces are present universally, regardless of the species and polarity of the interacting atoms or molecules. The forces can be attractive or repulsive, but mostly attractive and long-range, effective from a distance longer than 10 nm down to the equilibrium interatomic distance (about 0.2 nm). 

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