Ion-molecule interaction energies

Long-range electron- or ion-molecule interaction energy... 

Studies of the vibrational excitation of N2 ions in collisions with He gave a rough estimate of 0.026 eV for the ion-molecule interaction energy in HeN [10]. 

Intramolecular Isotope Effects. The data in Figure 2 clearly illustrate the failure of the experimental results in following the predicted velocity dependence of the Langevin cross-section. The remark has been frequently made that in the reactions of complex ions with molecules, hydrocarbon systems etc., experimental cross-sections correlate better with an E l than E 112 dependence on reactant ion kinetic energy (14, 24). This energy dependence of reaction presents a fundamental problem with respect to the nature of the ion-molecule interaction potential. So far no theory has been proposed which quantitatively predicts the E l dependence, and under these circumstances interpreting the experiment in these terms is questionable. 

Recent advances in experimental techniques, particularly photoionization methods, have made it relatively easy to prepare reactant ions in well-defined states of internal excitation (electronic, vibrational, and even rotational). This has made possible extensive studies of the effects of internal energy on the cross sections of ion-neutral interactions, which have contributed significantly to our understanding of the general areas of reaction kinetics and dynamics. Other important theoretical implications derive from investigations of the role of internally excited states in ion-neutral processes, such as the effect of electronically excited states in nonadiabatic transitions between two potential-energy surfaces for the simplest ion-molecule interaction, H+(H2,H)H2+, which has been discussed by Preston and Tully.2 This role has no counterpart in analogous neutral-neutral interactions. 

Statistical theories treat the decomposition of the reaction complex of ion-molecule interactions in an analogous manner to that employed for unimolecular decomposition reactions.466 One approach is that taken by the quasiequilibrium theory (QET).467 Its basic assumptions are (1) the rate of dissociation of the ion is slow relative to the rate of redistribution of energy among the internal degrees of freedom, both electronic and vibrational, of the ion and (2) each dissociation process may be described as a motion along a reaction coordinate separable from all other internal... 

The ion-dipole interaction energy is usually large so that the ion and the dipole align each other. The dissolution of ionic molecules in polar solvents (e.g., water) is due to the ion-dipole interaction (e.g., ZnCl in polyalcohol). When a dipole attracts toward an oppositely charged ion, the comparable ion-ion bond energy in the solid state is released. 

Ion-dipole interaction — One of the intermolecular interactions, which acts between an ion and dipoles such as water molecules. The ion-dipole interaction shows a significant stabilizing effect on the hydration or - solvation of ions (see -> hydrated ion). The interaction energy 1/i d between a dipole and an ion placed at a distance r from the dipole center is approximately given by... 

What is the expression for the energy of interaction between an ion of charge ZjCo and a quadrupole The derivation of a general expression requires sophisticated mathematical techniques, but when the water molecule assumes a symmetrical orientation (Fig. 2.35) to the ion, the ion-quadrupole interaction energy can easily be shown to be (Appendix 2.3)... 

When the ion is in contact with the water molecule, as is the case in the primary solvation sheath, expression (2.44) for the ion-quadmpole interaction energy becomes... 

If the minimum of the potential corresponds to an Na -O separation of 238 pm and a K -O separation of 278 pm, then the most probable distances in simulated clusters containing 6 water molecules are about 244 and 284 pm, respectively, at 300 K and about 2 pm less at 5 to 10 K. In Table 2.25, potential parameters that provide such results are given, and the dependence of the ion-water interaction energy on the ion-0 distance is shown in Fig. 2.63. 

When an comes in contact with water molecules, its ion-quadrupole interaction energy is -394.6 kJ mol . Calculate the quadrupole moment of water (r = 138 pm, rp- = 136 pm,n =. i D). (Contractor)... 

For a system having a Maxwell-Boltzmann energy distribution, current classical theories of ion-molecule interactions predict a collision or capture rate coefficient given by... 

Alkali-metal-ion-O-donor-solvent cages exhibit low-frequency bands in the i.r. spectrum characteristic of the cation-O polyhedra. Similar bands are seen with N-donors. The bands can be used to establish the nature of cation co-ordination and serve as probes to examine ion-solvent interactions.87 An analysis of the i.r. spectra of ternary mixtures LiClCX-Sj-Sz showed a preferential solvation of the Li+ ion by NH3 and methylamines (St) in MeCN or THF (S2) and by MeCN (S2) in MeN02 (SO. The appearance of wide bands in the ion-cage vibration region is related to the formation of different species [Li(Si) -i(S2)i]+. The Li+-solvent molecule interaction energy decreases when the number of S2 molecules in the first solvation shell increases. The mean composition of the first solvation shell was obtained from intensity measurements of the molecules not bonded to the ions in favourable cases (S2 = ND3 or MeCN), the solvation number of the Li+ ion in the pure solvent... 

If there are six water molecules in the inner-sphere hydration shell of Na" and AF , how much of the free energy of hydration estimated from equation 1.21 can be accounted for by inner-sphere hydration Is this a true estimate of the ion-dipole interaction energy Explain. 

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