Long-range potential dipole-molecule

For the case of a polar molecule having a permanent dipole D, the long range potential takes the form ... 

In the case where the target molecule has a permanent dipole moment, the expressions for the cross section in equations (20) and (21) must be modified fundamentally. The long range potential of a polar molecule behaves like that of a point dipole. 

In the separation of small molecules, including small biologically relevant species, HiU and co-workers have described the utility of tuning the selectivity of IM separations (elution order of analytes) on the basis of drift gas polarizability. In this case, the long-range potential between the analyte ion and drift gas is promoted in the form of ion-induced dipole interactions. The contribution of ion-induced dipole interaction to Kq is defined as the polarization limit, or Kp i, which represents the mobility of an ion, in a gas of particular polarizability, in the limit of vanishing energy and temperature... 

Pc- (c) Dipole density p. (d) Water contribution to the surface potential x calculated from the charge density Pc by means of Eq. (1). All data are taken from a 150 ps simulation of 252 water molecules between two mercury phases with (111) surface structure using Ewald summation in two dimensions for the long-range interactions. 

The possibility of a barrier which inhibits a reaction in spite of the attractive ion-dipole potential suggests that one should make even crude attempts to guess the properties of the potential hypersurface for ion reactions. Even a simple model for the long range behavior of the potential between neutrals (the harpoon model ) appears promising as a means to understand alkali beam reactions (11). The possibility of resonance interaction either to aid or hinder reactions of ions with neutrals has been suggested (8). The effect of possible resonance interaction on cross-sections of ion-molecule reactions has been calculated (25). The resonance interaction would be relatively unimportant for Reaction 2 because the ionization potential for O (13.61 e.v.) is so different from that for N2 (15.56 e.v.). A case in which this resonance interaction should be strong and attractive is Reaction 3 ... 

Early attempts to describe bimolecular gas phase ion-molecule reactions were based on the classical collision dynamics of a point charge and a structureless polarizable neutral molecule. The collision process is dominated by the long range attractive ion-induced dipole potential V(r) given by (16),... 

Multipolar induction. For the description of the long-range dipole components, we start with the electric potential at the distance R outside the molecule 1 [323, 391]. In a space-fixed coordinate system, the potential is given as... 

The purpose of this paper is to calculate the electrochemical potential and the double layer repulsion using a lattice model, applicable to hydrated ions of different sizes, that accounts for the correlation between the probabilities of occupancy of adjacent sites. As the other lattice models,4-7 this model accounts only for the steric, excluded volume effects due to ionic hydration. In feet, short-ranged electrostatic interactions between the ions and the dipoles of the water molecules, as well as the van der Waals interactions between the ions and the water molecules, are responsible for the formation of the hydrated ions. The long-ranged interactions between charges are taken into account through an electrostatic (mean field) potential. The correlation between ions is expected to be negligible for sufficiently low ionic concentrations. 

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