Interference spectrum

The influence of an impurity (Y) on the absorption spectrum of a substance (X) can often be eliminated by considering derivative curves as shown in Fig. 17.15 the second-order plot of the mixture is identical with that of pure X. When the interference spectrum can be described by an nth-order polynomial, the interference is eliminated in the (n+ 1) derivative. 

Figure 4. Reflectometric interference spectroscopy (RIFS) caused by constructive and destructive superposition of two partial beams being reflected at the two interfaces of a thin layer (300 nm - some pm), shift of the interference spectrum caused by a change in the optical thickness.

Fig. 7.10 Interference spectrum of the fs laser fabricated fiber inline FPI device. Insert interfer ence fringe plotted in dB scale. Reprinted from Ref. 18 with permission. 2008 Optical Society of America...

Upon selective absorption of analyte molecules from the ambient environment, the zeolite thin film increases its refractive index. Correspondingly, release of adsorbed molecules from the zeolite pore results in the decrease of its refractive index. The absorption/desorption of molecules depends on the molecule concentration in the environment to be monitored. Therefore, monitoring of the refractive index change induced phase shift in the interference spectrum can detect the presence and amount of the target analyte existing in the environment. 

Figure 7.14 shows the structure, microscopic images, and representative interference spectrum of the sensor. As shown in Fig. 7.14c, the two reflections... 

According to (7.7), the interference spectrum reaches its minimum (/min) when the phase of the cosine term becomes an odd number of it. That is... 

Photoelectron diffraction is most useful for systems where the photoexcited atoms all have the same local geometry, as in a chemisorption problem. If there are source atoms in different local geometries, there will be interference between multiple sets of scattering paths, and the resulting interference spectrum will be harder to interpret. For these cases LEED experiments are probably better, with diffuse LEED used for disordered systems. 

Fig. 16.11. Schematic of a porous silicon optical interferometric sensor [90]. Reflection of light from the porous surface and the porous-bulk interface yields an interference spectrum. Adsorption of species into the...

Fig. 5.65. Interference spectrum in reflection for modulation of reflected intensity at the interfaces of a thin film with wavelength of measurement. The shift of the extremum by changes of...

The change in the interference spectrum can be used to monitor photochemical processes taking place in solid matter, which influence the complex refractive index... 

An increase in optical thickness of the thin film, caused by e.g. ligand adsorption, will shift the interference spectrum to a higher wavelength and widen the distance between the minima and maxima in the inteference spectra as illustrated in Fig. 14.45b. This is the principle behind reflectometric interference spectroscopy, or Rifs [315]. Due to the high sensitivivity of the detection (ppm levels of phase shifts can be measured [316]), the RIfS device has been successfully used for the study of various biological interactions at surfaces, such as mouse anti-atrazine/ atrazine [317] and DNA-ligand interactions [318]. The principle of RIfS also allows the construction of low-cost devices. 

Figure 33. A) Reflected beams at a multilayer system (upper diagram) in which two beams (I) and (2) interfere constructively or destructively B) Resulting interference spectrum (lower diagram)...

Fig. 13. Provided the geometrical thickness is known, the corresponding dispersion curve can be computed from the interference spectrum measured (from Zeiss Information).

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