Dressed ions

Dressed ions carry electrons while slowing down. This feature is important for all ions below some characteristic speed A rough estimate for Vc is... 

Lacking progress in the theory of stopping of swift dressed ions had two serious reasons ... 

A dressed ion will repeatedly change identity due to charge exchange while penetrating through a medium. Therefore, precise definition of the stopping force... 

For more complex projectiles and targets, additional features become apparent in the spectra of ejected electrons. Doubly differential cross sections for ionization of CH4 by 0.3 MeV/u ions (3.6 MeV total projectile energy), taken from some of the author s unpublished work, are shown in Fig. 17 to illustrate the increasing complexity of dressed-ion collisions compared to that for bare ions represented in Fig. 9 by proton impact. In Fig. 17, the cross sections are seen to have their maximum at very low energy ejected electrons as was the case for proton impact, and, although their shape is not as sharp and... 

Figure 15 Total ionization cross sections due to dressed ion impact on water vapor. Cross sections for and He were adjusted to reproduce stopping powers for the lower energy protons and alpha particles. (Experimental data from Refs. 200, 213, and 217.)...

Fig. 4. Energy loss of ions (assuming frozen charge state conditions) as a function of the ion velocity r. The solid line is the result of the non-linear calculation for partially dressed ions (Z = 7, = 4). The dashed lines are the predictions of...

Finally, a cautionary note must be added. Wall distortion has not been considered. It is possible that the interaction between wall-dressed ions is much different than the bare interaction. In view of the blue-shifting dressing with wall phonons may yield, the ultimate interpretation of channel ionic vibrations in multiply occupied systems may be a challenge. 

Recently, Mohanty et al. have provided a resolution to this issue [90a]. In this approach, the polyion is regarded as a cylinder of radius R of contour length L immersed in a univalent salt solution. The ions are expected to be bound to the polyion due to the high value of the linear charge density , which for B-DNA is larger than 4. Consequently, the bound ions with the bare polyion are regarded as dressed. The free ions and the dressed ions can be viewed as an ideal mixture that interact via a Donnan potential [90a,91],... 

As we have seen, the spectra of electrons ejected from a target atom or molecule by dressed ions and neutrals are quite different from those induced by bare projectiles. These differences cannot be explained by use of a simple effective charge as was defined by stropping power theory. For fast relatively simple dressed ions, such as H° or He, the separation of target and projectile ionization is relatively straightforward. The single... 

The fundamental theories on EDL interactions have been substantially advanced by several researchers in the recent past in order to incorporate the effects of other pertinent physicochemical phenomena in the mathematical model and to generalize the underlying postulates. Kjellander and Mitchell [5] employed the dressed ion theory for EDL structure and interactions, which is nothing but an exact statistical mechanical formahsm for electrolyte systems. In their theory, the dressed ions took equivalent roles as the bare ions in the Poisson-Boltzmann approximation. A practical method was also derived for evaluating the effective surface charge densities of the particles. Behrens and Borkovec [6] proposed... 

Kjellander R, Mitchell DJ (1997) Dressed ion theory for electric double layer structure and interactions an exact analysis. Mol Phys 91 173-188... 

There have been other attempts to apply integral equations methods derived from Equation 3.51 or other similar expressions. One of them is the hypemetted chain (Henderson 1983), which is a generalization of the MSA theory, applicable to higher charge/potential values. It gives results comparable to the MPB ones but requires more extensive numerical evaluations. Another proposal is so-called dressed-ion theory of Kjellander and Mitchell (1994, 1997). 

Kjellander, R., and D. J. Mitchell. 1994. Dressed-ion theory for electrol)4e solutions A Debye-Huckel-like reformulation of the exact theory for the primitive model. The Journal of Chemical Physics 101, no. 1 603. doi 10.1063/1.468116. 

Another way of changing the effective coupling constant is to dress the bare ions in the beam with electrons. In certain circumstances, e.g., if the target electrons do not approach the projectile too closely, the dressed ion can act like a bare ion of effective charge q. 

This shows that although the th ion is treated with a finite radius, all others are considered as point ions. The obvious remedy, which can also be justified on statistical mechanical grounds according to dressed-ion theory is to replace Eq. [355] with the symmetric relation... 

Kjellander and co-workers to propose the dressed-ion theory (DIT) model, discussed briefly above, in which each primitive model ion is represented as a bare ion dressed in part of its surrounding ion cloud. 

GC Gouy-Chapman PB, Poisson-Boltzmann DH, Debye-Huckel ADH, apparent Debye-Hflckel NLDH, nonlinear Debye-Huckel PGC, perturbed Gouy-Chapman DIT, dressed-ion theory... 

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