Orientational scattering

Kleyn and collaborators have investigated the oriented scattering of NO from Ag(lll) by passing a rotationally cold supersonic NO molecular beam through a hexapole field prior to scattering from the surface [166-169]. They observe that... 

We shall assume, for simplicity, that we are dealing with a very dilute solution of identical particles with random positions and orientations. Scattering data, however, can also be interpreted for po-lydisperse solutions and in cases in which there are interparticle interactions. The intensity scattered in the forward direction by a solution of particles of concentration c2 is given by (Eisenberg, 1981) ... 

The PEO-aluminosilicate domains in the hybrid material have a larger volume fraction and incompatibility with the PEP and PHMA blocks than the PEO domains in the parent ABC copolymer. Thus, the hybrid materials and the parent copolymer can have different morphologies. Figure 21.10a shows a two-dimensional SAXS pattern from hybrid A in which the sample was oriented so that the normal to the film surface was directed along the y-axis (vertical). For this orientation, scattering along... 

Hollow u.nd solid sphere ( radially oriented scattering elements with cy 1 i nd ienl sym inetry )... 

I. C. Khoo, Y. Liang and H. Li, "Polarization Switching by Stimulated Orientational Scattering in Birefringent Nonlinear Nematic Liquid Crystal Film," lEEE-Lasers and Electro-Optics Society Technical Meeting, San Jose, CA (November 1993). 

The methods can principally be divided into two classes to investigate the properties of (a) reflected light and (b) diffuse or direction-oriented scattered light. 

The scattering from randomly oriented non-spherical inhomogeneities is isotropic. Oriented scatterers, however, result in an anisotropic scattering. Cargill (1972) observed an anisotropy in the small angle X-ray scattering from evaporated amorphous germanium films. From his results he concludes that the amorphous films ( 7 /xm thick) contain 1-2 volume % of rod shaped voids whose dimensions are 22 A X 46 A in the plane of the film and 2200 A normal to the film plane. 

Figure 14.22. Deconvolution procedure of the SAXS pattern of the 75/20/5 UDP MFC. (a) original SAXS image (b) intensity pattern of the isotropic scattering (c) intensity pattern of the oriented scatterers obtained by subtraction (a) - (b) [12]. The fiber ajds is horizontal [63]...

In Figure 14.23, three-dimensional (3D) visualization of the initial pattern (Figure 14.23(a)) and the oriented scattering (Figure 14.23(b)) for the same 75/20/5 composi-... 

HDPE/PA12/YP UDP MFC composition (wt%) Isotropic scattering Oriented scattering Isotropic scattering Oriented scattering ... 

Figure 14.25. Reconstructed SAXS patterns (oriented scattering) of two UDP MFC materials and their respective chord distribution functions. Fibril axis is vertical. The CDF function is presented in absolute values (both positive and negative faces in one image)...

Figure 14.27. Example of the analysis of the WAXS patterns at 30°C of HDPE/PA6/YP UDP MFCs. Left total scattered intensity Center calculated isotropic intensity Right oriented scattered intensity, (a) 80/20/0 and (b) 70/20/10. The fiber axis is vertical [63]...

Figure 14.28 shows the 3D images of the real WAXS patterns before treatment (left) and of the oriented scattering after subtracting (right) of the 80/20/0 and 70/20/10 MFCs. The white arrows indicate the position of the a-PA6 (200) reflection. This representation better shows the anisotropy of the HDPE (110) and (200) reflections. 

Figure 14.29. ID WAXS profiles of the 80/20/0 HDPE/PA6/YP UDP MFC exemplifying the peakfitting of the oriented scattering (a) and of the isotropic WAXS scattering (b) [63]...

Notes The coefficient / is the relationship between the PA12 and HDPE fractions of the oriented scattering ... 

From the oriented scattering pattern we compute the scattering power Q of the ideal semicrystalline morphology (no density fluctuations within the domains, no density transition zone between the domains) [3]. For this purpose we start from G S 2. s ) and extract the scattering intensity /isemicrystalline morphology. Then S3) = f lidisi, S2, S3) dss is computed. The equation presents the... 

The dynamics of orientational scattering has been discussed on various occasions in the preceding chapter. We shall discuss here the mechanism of Brillouin and Rayleigh scatterings. 

Accordingly, unlike most nonhnear optical materials, liquid crystals enable optical wave mixings to occur with high efficiency in the visible as well as infrared regime. In this section, we discuss two exemplary wave mixing processes in hquid crystals stimulated orientational scatterings and optical phase conjugation processes. 

Stimulated Orientational Scattering and Polarization Self-Switching Steady State... 

Figure 12.8. Experimental set up for observing stimulated orientational scattering in a nematic liquid crystal. Photos show the transmitted pump (e-wave) and stimulated (o-wave) at low and high input laser power.

In a recent study, the coupled electromagnetic waves and director axis reorientation equations, cf. Chapter 11, for the stimulated orientation scattering process are solved by treating all the molecular and optical parameters involved as spatial-temporal variables. For example, the director axis reorientation angle 0 is represented as 0(z,t)=2 (r)sin( 7tz/Z). In that case, the torque balance equation becomes... 

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