Polarized spectra

Boylan and Tripp [76] determined hydrocarbons in seawater extracts of crude oil and crude oil fractions. Samples of polluted seawater and the aqueous phases of simulated samples (prepared by agitation of oil-kerosene mixtures and unpolluted seawater to various degrees) were extracted with pentane. Each extract was subjected to gas chromatography on a column (8 ft x 0.06 in) packed with 0.2% of Apiezon L on glass beads (80-100 mesh) and temperatures programmed from 60 °C to 220 °C at 4°C per minute. The components were identified by means of ultraviolet and mass spectra. Polar aromatic compounds in the samples were extracted with methanol-dichlorome-thane (1 3). 

LB films prepared from an azabenzene-containing surfactant donor-TCNQ acceptor and transferred to solid substrates Absorption spectra, polarized microscopy, and conductivity measurements... 

The intensity relationships of the spectra polarized parallel and perpendicular to the C3 axis give an assignment of the components. Assignments of this kind are now available for tris-oxalates (95), tris-malonates (96), and tris-acetylacetonates (97). 

Fluorometers and fluorescence spectrophotometers are available that offer a variety of features. These features include ratio referencing, microprocessor-controlled excitation and emission monochromators, pulsed xenon light sources, photon counting, rhodamine cell for corrected spectra, polarizers, flow cells, front-surface viewing adapters, multiple cell holders, and microprocessor-based data reduction systems. 

The main problem in this investigation is to measure the critical particle size, where constant D becomes zero so that spectrum transforms into cubic symmetry one. As only the central transition was observable in the above powder, the value of D constant has been extracted from small distances between hyperfine lines. The contribution of the axial constant into latter lines appears only in the third order of perturbation theory with respect to small parameter DI g iBH), where g is electron g-factor, p,B is Bohr magneton and H is the external magnetic field. The numerical analysis of ESR spectra polarization and its dependence on the particles radii with respect to above factors, lead the authors of [51] to critical radius value equal to 50 nm for BaTiOs. 

Figure 3. Comparison between the theoretical (Dirac 8 functions) and experimental spectra polarized along the b axis of the 1-methyl thy mine crystaL Solid line electric vector of the incident radiation parallel to the b axis dashed hne electric vector of the incident radiation perpendicular to the b axis. Figure reprinted with permission from Ref. 35. Copyright John Wiley Sons.

In this chapter, a sensitive method for measurement by continuous-scan Fourier-transform infrared (FT-IR) spectrometry called polarization-modulation spectrometry is introduced this is a useful method for measuring, with high signal-to-noise ratio, not only the reflection-absorption spectra of thin films adsorbed onto metal substrates but also other spectra such as vibrational circular dichroism (VCD) spectra. Polarization-modulation spectrometry is a type of double-modulation FT-IR spectrometry [1], In this chapter, descriptions of double-modulation spectrometry are given first, then polarization-modulation spectrometry is discussed, and then its application to the measurement of reflection-absorption spectra of thin films on metal substrates is discussed. 

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