Retarding lens

Figure 5. A horizontal schematic cut through the EMS spectrometer showing the monochromated and collimated incident beam and the hemispherical (fast) and toroidal (slow) energy and angle dispersive analysers as well as the retarding lens systems.

Reactant-ion energy analyzer. An electric sector or a retarding lens (or some combination of these) is generally employed to define the translational energy of the ion beam. 

In order to demonstrate the convenient properties of lenses combined with an electrostatic energy analyser, three examples will be discussed first the important case in which an acceleration/retardation lens is placed in front of the analyser which allows an operation mode with a constant pass energy in the analyser second the case in which increased acceptance angles are used, which is important for coincidence experiments and third the case in which 0 eV electrons are handled and analysed with high resolution and high acceptance. 

Figure 24.27 Schematic diagram illustrating the basic design of an x-ray photoelectron spectrometer using a retarding lens system and a hemispherical electrostatic analyser. (From P. M. A. Sherwood in Spectroscopy, vol. 3. B. P. Straughan and S. Walker, eds. London Chapman and Hall, Ltd., 1976.)...

Figure 5 Small spot XPS system using a monochromated focused x-ray source, demagnification retardation lens and a parallel data acquisition system, (after reference 13).

For the production of very slow ions, a retarding lens system must be used, as the production of the incident ions usually takes place at high energy. Such a lens system has been described by Futrell and Miller. The lens system used in the Stockholm apparatus is shown in Fig. 5. 

Fig. 5a. Retarding lens system according to Lindholm. The voltages indicate the kinetic energy of the ion and are given for four different energies after the retardation from 1000 to 30 eV (I), 100 eV (II), 300 eV (III), and 900 eV (IV). Electrode h is split and electrode j is used for focusing. The electrodes are drawn to scale. In order to permit pumping, the electrodes h and i are made from mesh.

Cystathionine fisynthase (EC 4.2.1.22). Failure to form cystathionine from homocysteine and serine. Elevated homocysteine and methionine in serum. Urine contains homocystine and homocysteine-cysteine disulfide. Cystathionine virtually absent from brain, where it is normally present in significant quantities. Mental retardation. Lens detachment. Skeletal abnormalities (tall stature, arachnodactyly). Arterial and venous thrombosis. 

Sulfite oxidase (sulfite dehydrogenase) (EC 1.8.3.1). Urinary excretion of S-sulfo-L-cysteine, sulfite and thiosulfate, and virtual absence of urinary sulfate. Progressive neurological abnormalities, mental retardation, lens dislocatioiL Treatment with diet low in sulfur amino acids. Death in postnatal period possi-... 

---