Ion-induced polarization

The first channel is formally endoergic charge transfer, which can occur through a variety of mechanisms. For example, in large impact parameter collisions, the time-dependent ion-induced polarization can result in electron hopping from C o to the M ion. This mechanism has been investigated for several atom-cluster ion systems [22], and is only efficient when the following condition is satisfied / AIP—hv, where AIP IP(CM) IP(Af)> v is the relative velocity of the M ion to the Cgo, and R is... 

Cation-Jt-interactions are noncovalent binding forces with great importance in many systems. Ab initio calculations were performed on complexes between cations and j-triazine, which has a small and positive quadrupole moment. Minimum-energy Jt-complexes were found between j-triazine and cations (Figure 2). A likely explanation of this duality is the stabilization obtained from the ion-induced polarization <2003OL2227>. 

An ion-induced dipole force results when an ion in close proximity to a non-polar molecule distorts the electron density of the non-polar molecule. The molecule then becomes momentarily polarized, and the two species are attracted to each other. This force is active during every moment of your life, in the bonding between non-polar O2 molecules and the Fe " ion in hemoglobin. Ion-induced dipole forces, therefore, are part of the process that transports vital oxygen throughout your body. 

A dipole-induced dipole force is similar to that of an ion-induced dipole force. In this case, however, the charge on a polar molecule is responsible for inducing the charge on the non-polar molecule. Non-polar gases such as oxygen and nitrogen dissolve, sparingly, in water because of dipole-induced dipole forces. 

Ab-initio SCF calculations on the water molecule in various model complexes such as (H20)2, Li+H20, and (Li+)2 H20 show a depletion of the density of the lone pair in the internuclear region for long bonds, while for short bonds, such as Li+ O < a 1.6 A and O(H) O < 2.6-2.7 A, the effect is found to be reversed (Hermansson 1985), in accordance with the observations on oxalic acid dihydrate. The induced polarization of the acceptor density towards the Li+ or H atom is apparently still present for the longer distances, but very diffuse and below the lowest contour of most maps (D. Feil, private communication). Exchange repulsion opposing the attractive effect becomes important for larger ions such as K+, for which the oxygen lone pair penetrates the ion s electron... 

Ion-induced dipole-a polar solid and polarizable adsorbate. 

Figure 3. Different mechanisms for inducing polarization through (a) redistribution of electron density, (b) bond stretching, (c) alignment of dipoles, and (d) separation of ions.

We consider the so-called Langevin model for ion-molecule reactions. An ion and a neutral non-polar molecule interact—at large distances—through an ion-induced-dipole potential... 

For example, carbon tetrachloride, CCU, has polar bonds ion-induced dipole js Q nonp0 ar molecule due to the symmetry of those... 

The induced dipole moment depends on the electric field strength and the structure of the molecule. Charge-induced dipole interactions occur between a charged ion and polarized molecules. A molecule possessing conjugated double bonds is readily polarized. Examples of solutions due to the dipole-induced dipole interaction are benzene in methanol, chloral hydrate in CC14, and phenol in mineral oil. 

The similarity in the adsorption behavior of krypton on the three kinds of mica surfaces suggests that the adsorption here is primarily due to dispersion forces, with very little contribution from ion-induced dipole forces. The results of Barrer and Stuart (1) for the adsorption of argon on various ion-exchanged forms of faujasite are similar. They found that while calcium, strontium, and lithium faujasite—i.e., the materials containing cations with greater polarizing power—did show heat effects correlatable with ion-induced dipole interactions, no such effects were observed with sodium, potassium, or barium zeolites. With the latter materials, they also concluded that the adsorbed argon possessed appreciable mobility. 

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