Medium electrostatic analyzer

More work is needed to clearly establish the role of outer-sphere association in DNA-platination. We can infer its influence on the rate of platination according to the relation kp = kK0 [N]/(l + K0 [N]) (with N = nucleotide-binding sites of Pt, i.e., N G, [N] [Pt]) (Scheme 3). It could also influence the selectivity of platination via selective association between the cationic species and the sites of higher negative electrostatic potential. To test this hypothesis one will have to analyze the influence of various sequences, of different types of platinum ligands, and of the ionic status of the DNA medium. 

Fig. 15.3. Medium current beamline showing an electric scanner and electrostatic parallelizing lens. The ion source, analyzer magnet, and resolving aperture serve to inject the unscanned beam from the left. The parallel scanned beam on the right is passed through a postacceleration column and an electrostatic deflector before reaching the wafer...

The electrostatic model proposed by JW was later thoroughly analyzed in a series of works performed by the Swedish-Australian group (17-19), where exact formal treatment and approximate methods were used to solve the problem. The authors of these papers considered two electrostatic models. In the first model they investigated the interaction between two planar surfaces (separated by a distance h) with mobile ions adsorbed onto them (the net surface charge was zero). The surfaces were immersed in the dielectric continuum with the dielectric constant eP Behind each surface a different dielectric medium (with the dielectric constant e2) was placed. In the second model the mobile ions were replaced by mobile dipoles that were oriented perpendicular to the surfaces. In both models the motion of the particles was restricted to the well-defined plane. From the analytical treatment, which included images and correlations, the following asymptotic results for the pressure were obtained for the first model ... 

The simple virtual charge model discussed by Constanciel and Tapia [6] has been developed into an extended generalized Born (EGB) approach. Different approximations have been proposed. Constanciel [40] has analyzed the theoretical basis used as foundations for empirical reaction field approximations through the continuum model to the surrounding medium. Artifacts in the EGB scheme have been clearly identified. The new approximate formulation proposed derives from an exact integral equation of classical electrostatics following a well defined procedure. It is shown there how the wavefunction of solvated species imbedded in cavities formed by interlocking sphere in a polarizable continuum can be computed. 

Fig. 8.2. Potentials bold lines) along different H/FD ion sources to realize full extraction voltage while delivering ions of defined kinetic energy to the analyzer. The part numbers correspond to 1 emitter, 2 counter electrode, 3 optional electrostatic lenses, 4 analyzer entrance slit, (a) Instruments with high acceleration voltage, (b) instruments with medium acceleration voltage as is often the case in magnetic sector instruments, and (c) instruments requiring slow ions, e.g., FT-ICR or oaTOF instmments.

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