Orientation sensitivity

Voyiatzis and Andrikopoulos discuss adding an orientation-sensitive, resonant Raman additive to a polymer mixture prior to drawing in order to calculate molecular orientation continuously. The approach was tested with poly(vinyl chloride) (PVC), isotactic polypropylene (iPP), and poly(vinylidene fluoride) (PVF2). The ratio of a band from the additive to the orientationally insensitive CH2 bending mode at 1435 cm-1 in the polymer was computed. While the addition of such an additive is unreasonable for many industrial processes, the authors note a favorable alternative for industrial PVC samples. 

Dash several hours, yields deep etch pits on all orientations sensitive to oxygen impurity 3191. 020... 

To increase the SNR of the method, remove absorption from the atmosphere, and reduce the baseline distortions, in 1993 Desbat and co-workers [569, 585] introduced PM (Section 4.7) in IRRAS of the AW interface. PM-IRRAS requires the set-up depicted schematically in Fig. 4.52, in which the IR beam is directed from the PEM onto the water surface, and the reflected beam is redirected to the MCT detector with two flat mirrors. The most appropriate from the viewpoint of both surface and orientational sensitivity (Section 3.11.5) is the angle of incidence of 75° [569]. PM provides a good SNR in the spectra acquired within 5-10 min with a 4-cm resolution. 

The chemical and orientational sensitivity of nexafs spectroscopy has been used for analysis in a variety of applications. Examples of studies involving nexafs spectroscopy are given below ... 

In the context of this presentation we will be much more mundane and investigate only changes between integral valences as they occur in the course of surface reactions. We emphasise thus the surface sensitivity of CEELS as opposed to the more bulk oriented sensitivity of XAS. Oxidation reactions provide most illustrative examples, and the oxidation of Yb, Eu and Ce will be considered here. As mentioned before the characteristic multiplet structure of 4d excitations is particularly well suited as fingerprint of the 4f count. But also 3d and 4p excitation profiles exhibit changes that correlate with changes of the f count. 

The efficiency of PL polarizers is chiefly limited by the luminophore s quantum yield which, ultimately, can approach unity, but for PL polymers typically is up to 80 % (24,33). However, when used in a standard PL LCD configuration (see above), only 50 % of light incident from the light source is used, since the absorption of these PL polarizers is also anisotropic (74-25). We recently have demonstrated a new concept for polymer-based PL polarizers which overcome this limitation and can be used in PL LCDs with, in principle, an ultimate efficiency of unity (34,35). These PL polarizers comprise a nearly randomly oriented sensitizer that maximally harvests light by isotropic absorption, efficiently transfers the energy to a uniaxially oriented PL polymer which, subsequently, emits highly linearly polarized light. Key step is a... 

It is possible to determine the orientation of the polymer molecules in the coating relative to the metal surface. In the same fashion as dichroic measurements are made, the ratio between a spectrum with parallel-polarized radiation and a spectrum with perpendicular-polarized radiation is calculated in order to determine the molecular orientation. In some cases, this orientation sensitivity is also helpful in making band... 

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