Retarding potential analysis

Fig. 3. The pulsed ejection of product ions from the collision chamber using a pulsed, longitudinal tandem mass spectrometer. The positive ejection pulse is applied to the entrance slit of the collision chamber immediately after the primary ions have left the collision chamber. The figure shows the energy analysis of the product ions (by retarding potential analysis) observed under two conditions ...

Energy distributions are conveniently measured using retarding potential analysis (Chapter 12). Residence time distributions are measured by pulse techniques. ... 

Retarding potential analysis of reactant or product ions issuing from the collision chamber can be performed using the grid system constituting the ion optics following the collision chamber. 

Selection of Fire Retardants. The choice of flame retardants depends on the nature of the polymer, the method of processing, the proposed service conditions, and economic considerations. Although the processing, service, and economic factors are impor.pa tant, the flame-retardancy potential of an additive is of primary importance, and this factor can be readily evaluated by thermal analysis. 

Spin analysis was carried out by a Mott-scattering detector with a spherically symmetric acceleration field operated at typically 70 keV without retarding potentials [3]. Surface barrier detectors were used as electron detectors. The figure of merit x ///q amounts to about 2.4 x 10 ". The advantages of this type of... 

Fig. 7. Energy analysis by the retarding potential technique of argon primary ions produced in a standard mass-spectrometer ion source operated with a dc repeller field. The shape of the curve should be independent of the ion exit energy E data shown for three different values of E demonstrate this in the appropriately normalized plot. The distribution of experimental ion exit energies results from the finite thickness of the electron beam, and the figure shows theoretical distributions predicted for various assumed thicknesses of the electron beam. Fair agreement is found for an assumed thickness of 0.5 mm, the actual dimension of the slit through which the electron beam enters the source.

Pig. 3.4 Retarding field analysis for size-selected clusters deposited in the UHV chamber measured current (blue) as a function of the retarding potential, the kinetic energy (derivative, orange) and the velocity distribution (green)... 

Therefore, the cluster catalysts need to be deposited onto the support under so called soft landing conditions at deposition energies lower than 1 eV/atom [6, 11, 28]. These conditions can be ensured by a retarding field analysis (RFA), where the cluster current is measured as function of an applied retarding potential on the samples. Figure 3.4 shows a representative RFA for size-selected Ft/j clusters. 

CE is also potentially a useful alternative analytical tool for monitoring of chemicals (dyes, flame retardants and lubricants) involved in various steps of the textile fibre manufacturing process. In this area, CE compares favourably with existing techniques. CZE-MSn was used for the analysis of sulfonated azo dyes [942]. A variety of fluorescent analytes including thiazole orange dyes have been characterised by CE-FLNS [943]. 

The above thermal analysis studies demonstrated the enhanced thermal stability of POSS materials, and suggested that there is potential to improve the flammability properties of polymers when compounded with these macromers. In a typical example of their application as flame retardants, a U.S. patent39 described the use of preceramic materials, namely, polycarbosilanes (PCS), polysilanes (PS), polysilsesquioxane (PSS) resins, and POSS (structures are shown in Figure 8.6) to improve the flammability properties of thermoplastic polymers such as, polypropylene and thermoplastic elastomers such as Kraton (polystyrene-polybutadiene-polystyrene, SBS) and Pebax (polyether block-polyamide copolymer). 

---