Range of layer charges

De Neve et al. (2000) have carried out a feasibility study to investigate the possibilities and limitations of CPAA as a thin layer characterization method (rather than for the determination of elemental concentrations in bulk samples). The required experimental conditions are (a) that the surface layer containing the analyzed element is thinner (1 pm or less) than the range of the charged particles used and (b) that the substrate (i.e. the layer on which the thin layer is deposited) does not contain the element(s) to be analysed. 

CPAA measures the characteristic decay radiation of the radionuclides produced by the incident charged particles. The technique has been widely applied in the determination of trace elements concentrations in bulk samples, but it also has possibilities for surface characterisation, provided the thickness of the layer to be characterised is less than the range of the charged particles employed. 

Another important function of these two features is the reduction of convection currents directly below the evaporation layer. This insures that the composition of the liquid at the liquid-gas interface reaches a steady state such that the composition of vapor and of the liquid flowing into the boiler become identical. The time required to achieve this state will depend upon the boiling range of the charge and the conditions at the interface. 

Figure 2.81. The self consistently calculated electrostatic potential due to an S and a K atom chemisorbed at the calculated equilibrium distance (1.9 and 4.0 bohr, respectively) outside a jellium (r = 2) surface. The potential is that felt by an electron at a lateral distance of 5 bohr from the atom and it is shown as afunction of distance outside the jellium edge, which is half an interlayer spacing outside the first metal layer. In order to give an idea of the range of the charge transfer to a chemisorbed molecule at its equilibrium position outside a Ni (100) surface occupies the region from approximately 2 to 4 bohr in the figurel l.

CPAA for surface characterization is based on irradiation of a thin surface layer, i.e., the thickness of the surface layer ( nm to pm) is much lower than the range of the charged particles used ( mm). Moreover, the substrate (i.e., the layer on which the... 

The great advantage of the RDE over other teclmiques, such as cyclic voltannnetry or potential-step, is the possibility of varying the rate of mass transport to the electrode surface over a large range and in a controlled way, without the need for rapid changes in electrode potential, which lead to double-layer charging current contributions. 

The Hg/dimethyl formamide (DMF) interface has been studied by capacitance measurements10,120,294,301,310 in the presence of various tetraalkylammonium and alkali metal perchlorates in the range of temperatures -15 to 40°C. The specific adsorption of (C2H5)4NC104 was found to be negligible.108,109 The properties of the inner layer were analyzed on the basis of a three-state model. The temperature coefficient of the inner-layer potential drop has been found to be negative at Easo, with a minimum at -5.5 fiC cm-2. Thus the entropy of formation of the interface has a maximum at this charge. These data cannot be described... 

---