Results Obtained from Optical Spectroscopy

Optical techniques have provided valuable information on many important properties of surface sihcides. The most common optical experiments include reflectance (R), transmittance (T), and elipsometric spectroscopy (SE). Although the physical process is the same, the method used to extract the optical functions from the experimental R, T, or SE measurements is different in the case of thin films, where the properties of the film itself and its purity and crystalline quality play a relevant role in the reliability of the optical constants determined. In particular, the results obtained from optical measurements on thin films can be affected by several contributions originating from the presence of the substrate. For qualitative analysis, it is sufficient to identify the spectral features of the substrate and normalize the measured spectra to this contribution. However, interference effects may also play... 

The results of the optical spectroscopy studies into sulfur vulcanisation of polydiene rubbers correspond well with the results obtained via low molecular weight model olefin studies and solid state 13C NMR studies. From all these studies the mechanism for accelerated sulfur vulcanisation as shown in Figure 6.2 has emerged [14-18], which is... 

Measuring the IPCE is also useful to determine the band gap. The band gap derived from IPCE may be higher than that obtained by optical spectroscopy techniques (see Chapter UV-Vis Spectroscopy ), since the onset of photocurrent may be limited by slow kinetics ( /interface) and/or electron transport ( /transport) This will have a minimum uncertainty of half of the wavelength step or bandpass (full-width at half maximum, or FWHM) used. Performing IPCE while applying a constant bias often increases the measured photocurrent, which could be due to either a shift of the Fermi level at the CE (not applicable in a three-electrode measurement) or due to increased carrier collection at the WE as a result of an increased depletion width. 

The HS LS relaxation is basically a unimolecular process, and in diluted mixed crystals corresponding relaxation curves are single exponential. In Figure 5, HS LS relaxation rate constants for several spin-crossover complexes doped into inert host lattices as well as for some LS complexes are plotted as Lhl on a log scale vs. l/T. Figure 5 includes data obtained by optical spectroscopy, by Mossbauer line shape analysis, and by Mossbauer emission. Above 50K, these curves show the classical behavior of a thermally activated process, as is expected based on the energy barrier between the two states, and in agreement with results from... 

Another TL application is the analysis of the electronics states in materials, which are defined by both material and technology of its production. For example, for PS different contact methods to define the electronics states in metal/PS stmctures have been aheady applied thermally stimulated depolarization currents (TSDC) and thermally stimulated current (TSC) (Ciurea et al. 1998 Anastasiadis and Triantis 2000 Brodovoy et al. 2002), optical charging spectroscopy (OCS) (Ciurea et al. 2000), and deep-level transient spectroscopy (DLTS) (Pincik et al. 1999 Tretyak et al. 2003). The mentioned methods determine the parameters of traps related with both PS material and metal/PS interface and often differ from results obtained from TL experiments. Two advantages of the TL method are that it is contactless and it can reveal the energy distribution of both bulk and/or surface states. The obvious drawback of TL is that it can only be applied to luminescent materials. 

Ayyalasomayajula et employed LIBS for the analysis of slurry samples. Three calibration models were developed using univariate calibration, multiple linear regression (MLR) and PLS. The LIBS analytical results obtained from the PLS model best fit the results obtained from inductively coupled plasma optical emission spectroscopy (ICP-OES) analysis. 

The results obtained from viscosity to characterize the unfolded state are presented in Chapter 5. In the present section, the data obtained by optical methods currently used in the study of the transition between native and denatured proteins are briefly discussed. Various reviews describe spectrophotometric methods and their use in the conformational studies of proteins (Wetlaufer, 1962 Hermans, 1965 Herskovits, 1967 Donovan, 1969b, 1973 Yon, 1969 Chen, 1967 Weber and Teale, 1965 Chen et ai, 1969 Lehrer and Fasman, 1967). Ultraviolet difference spectroscopy is the most current method used to study conformational transitions of proteins. When a protein undergoes a conformational transition from the native to the unfolded state, several chromophoric groups are transferred from the interior of the protein to the solvent. The alteration of their environment is accompanied by a small variation of the absorption spectrum, which is shifted in wavelength (A>1) and in intensity (As). The variation of intensity is in first approximation given by the first derivative of the absorption spectrum... 

In the optical spectroscopy experiments, data on the isotope shifts (IS) may be obtained in addition to those on the hfs. The important nuclear information on the changes of mean square charge radii, deduced from the IS results, will be discussed by Kluge at this symposium [KLU85]. 

From the late 1960 s to the early 1970 s, more direct approaches to the investigation of protein dynamics were intensively developed. Such investigations featured the application of physical methods, such as physical labeling, NMR, optical spectroscopy, fluorescence, differential scanning calorimetry, and X-ray and neutron scattering. The purposeful application of the approaches made it possible to obtain detailed information on the mobility of different parts of protein globules and to compare this mobility with both the functional characteristics and stability of proteins, and with results of the theoretical calculation of protein dynamics. 

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