Differential interferometry

As indicated, the specific refractive index increment is best measured by differential refractometry or interferometry. Experimental procedures as well as tabulated values of dn/ dc for many systems have been presented elsewhere40,63K The relevant wavelength and temperature are those used for LS. The value of X0 is invariably 436 or 546 nm, but with the advent of laser LS, values of dn/dc at other wavelengths are required. These can be estimated with good reliability using a Cauchy type of dispersion (dn/dc a 1/Xq). For example the values of dn dc for aqueous solutions of the bacterium T-ferrioxidans at 18 °C are 0.159, 0.141 and 0.125 ml/gm at X0 = 488, 633 and 1060 nm respectively64 ... 

This result is consistent with Whittaker s main conclusion [27,28], that the scalar potential is structured and physical in the vacuum, leading to the possibility of interferometry between different scalar potentials, without the presence of fields. To reinforce this conclusion, we can differentiate Eq. (484)... 

When two fluid interfaces have a high radius of curvature, such as in the pseudoemulsion film, the distance between the interference patterns is too small to be measured by common reflected light interferometry. In this case, differential interferometry can be used for imaging the interface profile [40-45]. (Another technique for studying curved films is the controlled drop tensiometer, as was shown in section 2.)... 

Applications of cantilevers also allows label-free detection of aptamer-ligand interactions. Although it is not an optical sensor, the interferometry is used for detection of the differential bending between cantilever and reference modified with non-specific aptamer [74],... 

Nafie LA, Diem M (1979) Theory of high-frequency differential interferometry - application to the measurement of infrared circular and linear dichroism via Fourier-transform spectroscopy. Appl Spectrosc 33 130-135... 

Three different configurations of oil droplets were observed by using differential (DI) interferometry (18,32) (Figure 7). Firstly there are oil droplets separated with a thick film from the air-water surface. This configuration of oil was very common for C AOS approximately 60% of the oil for this surfactant was present in this configuration, separated by the pseudoemulsion film. For C-.AOS this oil amount was approximately 40% and less than 20% for C AOS. 

Differential interferometry in reflected light allows measurement of the shape of the upper reflecting surface. This method was used by Nikolov et al. - " - "" to determine the contact angle, film and line tension of foam films formed at the top of small bubbles floating at the surface of ionic and nonionic surfactant solutions. An alternative method is the holographic interferometry applied by Picard et to study the properties of bilayer lipid membranes in solution. Film... 

We have constructed a new surface-force apparatus capable of measuring the capillary pressure and structural disjoining pressure of the thinning curved emulsion film as a function of time and film thickness (11-16). This apparatus is equipped with Max Zhender differential interferometry... 

Quantum gravity gradiometers based on atomic interferometry provide high sensitivity for the high resolution mapping of mass distribution above and below the surface of the earth (see Sect. 9.1.7). They can be used in the lab as ground-based version or in a satellite as space-born system. They measure differential acceleration with high precision. Their basic principle is shown in Fig. 10.27 [1487]. 

Ferretti A, Prati C, Rocca F (2000) Non-linear subsidence rate estimation using permanent scatter in differential SAR Interferometry. IEEE Trans Geosci Remote Sens 35(5) 2202-2212... 

Ge, D.Q. et al. 2007. A study of surface deformation monitoring using differential SAR interferometry technique and an analysis of its key problems. Remote Sensing for Land Resources, December 2007, 4(74) 14-22. 

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