Prism immersion

Table 1. Details of gratings appearing in Fig. 9. The names in parenthesis refer to the actual gratings delivered with GMOS-N (except for R150 which is slightly different) is the vertex angle of the immersed prism if present.

Modifications of existing differential refractometers have been made for precise evaluation of dn/dc at high X0, which has been particularly necessary where values at other wavelengths are not known. The apparatus of Jennings et al.64) is based on the immersed prism technique of Debye (also used in the commercial Shimadzu-... 

Figure 9. Predicted resolving power for CMOS equipped with the gratings described in Table 1 and slit width 0,5 arcsec. Those prefixed by X are hypothetical immersed gratings with prism vertex angle, (j>, given in the Table 1. The dots mark the nominal blaze condition. The box marks the requirements for measuring the velocity dispersion of dSph galaxies using the Calcium triplet.

Figure 10. Ray-tracing through an immersed grating suitable for CMOS with p = 1800/mm, with a 35-deg prism for 630 < A < 682nm.

Recently the wall-PRISM theory has been used to investigate the forces between hydrophobic surfaces immersed in polyelectrolyte solutions [98], Polyelectrolyte solutions display strong peaks at low wavevectors in the static structure factor, which is a manifestation of liquid-like order on long lengths-cales. Consequently, the force between surfaces confining polyelectrolyte solutions is an oscillatory function of their separation. The wall-PRISM theory predicts oscillatory forces in salt-free solutions with a period of oscillation that scales with concentration as p 1/3 and p 1/2 in dilute and semidilute solutions, respectively. This behavior is explained in terms of liquid-like ordering in the bulk solution which results in liquid-like layering when the solution is confined between surfaces. In the presence of added salt the theory predicts the possibility of a predominantly attractive force under some conditions. These predictions are in accord with available experiments [99,100]. 

Let us dwell on Figure 6.4 for a moment. The standards and sample solutions are introduced to the instrument in a variety of ways. In the case of a pH meter and other electroanalytical instruments, the tips of one or two probes are immersed in the solution. In the case of an automatic digital Abbe refractometer (Chapter 15), a small quantity of the solution is placed on a prism at the bottom of a sample well inside the instrument. In an ordinary spectrophotometer (Chapters 7 and 8), the solution is held in a round (like a test tube) or square container called a cuvette, which fits in a holder inside the instrument. In an atomic absorption spectrophotometer (Chapter 9), or in instruments utilizing an autosampler, the solution is sucked or aspirated into the instrument from an external container. In a chromatograph (Chapters 12 and 13), the solution is injected into the instrument with the use of a small-volume syringe. Once inside, or otherwise in contact with the instrument, the instrument is designed to act on the solution. We now address the processes that occur inside the instrument in order to produce the electrical signal that is seen at the readout. 

The prism and shde may be optically coupled with glycerol, cyclohexanol, or microscope immersion oil, among other liquids. Immersion oil has a higher refractive index (thereby avoiding possible TIR at the prism/coupling liquid interface at low incidence angles), but it tends to be more autofluorescent (even the extremely low fluorescence types). 

The observations are performed with a Leitz Ortholux polarizing microscope equipped with the ftOpak illuminator, lamps for reflected and transmitted light, immersion objectives, and verniers. Characteristics of the polished thin sections and of the nuclear emulsion plates are observed in transmitted light with the same immersion optics after removing the Berek prism. 

The measured spectral resolution of the new grating micro-spectrofluorometer is about 1 nm and preliminary trials show that the luminosity is improved by at least ten-fold as compared to the older Ultropak-prism-microspectrofluorometer. The acquired increased sensitivity is best exploited using objectives and immersion oils of low intrinsic fluorescence. 

A similar experiment was run with expansion test prisms immersed in 2.5% Na2S04 solution with the same results, although the reaction was slower. No significant prism length changes occurred during the immersion period. 

The most precise type of refractometer is the immersion refractometer. It contains a prism fixed at the end of an optical tube containing an objective lens, an engraved scale reticule, and an eyepiece. It also contains an Amici compensating prism (see below). In use, the instrument is dipped into a beaker of the liquid clamped in a water bath for temperature control. A mirror in the bath or below it reflects light into the bottom of... 

The most commonly used form of refractometer is the Abbe refractometer, shown schematically in Fig. 11. This differs from the immersion refractometer in two important respects. First, instead of dipping into the liquid, the refractometer contains only a few drops of the liquid held by capillary action in a thin space between the refracting prism and an illuminating prism. Second, instead of reading the position of the critical-ray boundary on a scale, one adjusts this boundary so that it is at the intersection of a pair of cross-hairs by rotating the refracting prism until the telescope axis makes the required angle 8 with the normal to the air interface of the prism. The index of refraction is then read directly from a scale associated with the prism rotation. 

Figure 9.17 The principle of a spectrophotometer fitted with an immersion probe. Monochromatic light issuing from a spectrophotometer is guided towards an immersion cell and then returned to the detector. The route is confined by a fibre optic. Left transmission probe. Right ATR probe the sapphire prism has a refraction index greater than that of the solution. The schematic shows three reflections of the beam and its penetration into the solution (see explanation in Chapter 10, Section 10.9.3).

Brewster s law. Reflected light in general is more polarised than the incident light and according to Brewster s law, the polarisation is maximum when i + r = 90 where i and r are the angles of incidence and refraction. There are several methods described in the literature such as those based on the use of prisms and fluid immersion (in fluids of known refractive indices) and index matching. The so-called Becke line technique for index matching uses observations under microscope. 

Model experiments were carried out to study the relation between friction and kinetics of electrochemical processes occurring during polarization of metal-polymer pairs [62]. The experiments employed a pendulum tribometer 1 (Fig. 4.14a) whose advantage is the presence of only one friction pair for examination at a time. The tribometer consists of a pendulum 2, a support 3, and a prism 4 on which the pendulum hangs. Support 3 is made as a vessel containing an electrolyte into which the friction surface in the form of one of the prism faces is immersed. The pendulum is set in motion at a constant initial amplitude. Attenuation of oscillations is recorded in terms of contracting amplitudes of the sinusoidal signal from the inductive pickup 6, into which the bow-shaped core 5 is in turn inserted as the pendulum oscillates. 

In evaluating Debye s factor H (equation 16), the refractive index increment of the solute must be accurately known. This determination is conveniently carried out with the differential refractometer of P. P. Debye (1946), in which the solution is contained in a hollow glass prism of triangular cross section, immersed in a cell containing the pure solvent. The deflection of a light beam passing through the system is a nearly linear function of the refractive index difference n — n0, which may thus be measured to about 0.000,003. 

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