Polar directional properties

Fig. 8-55 Overview of RPs directional properties (a) polar directional, (b) different fiber orientations and tensile fracture characteristics, and (c) stress vs. strain diagrams of RPs.

In contrast to spontaneous emission, induced emission (also called stimulated emission) is coherent, i.e. all emitted photons have the same physical characteristics - they have the same direction, the same phase and the same polarization. These properties are characteristic of laser emission (L.A.S.E.R. = Light Amplification by Stimulated Emission of Radiation). The term induced emission comes from the fact that de-excitation is triggered by the interaction of an incident photon with an excited atom or molecule, which induces emission of photons having the same characteristics as those of the incident photon. 

Just as polarized light enhances the utility of optical microscopy in the study of polymorphic systems, so polarization can be used in conjunction with IR spectroscopy. As we shall show later in greater detail (see Section 6.3.2) polarized spectroscopic methods provide detailed information on the directional properties which distinguish the spectral features of polymorphs. Thus, for instance, the directional properties of a polymorphic transformation of fatty acids (Kaneko et al. 1994a-c) and inferences about the differences in packing modes (Yano 1993) have been investigated with polarized IR methods. 

The directional properties of the naphthalene absorption system pointed to interpenetrating allowed and vibrationally induced bands, the former long-axis and the latter short-axis polarized. There did, however, remain a difficulty. Given the different polarizations the separation between the true and false origin(s) must be the frequency of a nontotally symmetrical vibration. The observed hot band separation however was close to a ground state Raman-active 512 cm-1 vibration, known with certainty to be totally symmetrical. 

Consider first the polar direction when 0 = 0 in (18). Then, due to the known property of spherical harmonics [70]... 

The geometrical shape of a novel aperture like SNOM probe influences the imaging properties of photonic nanostructures. By using triangular shaped aperture probes a selection of the position of the electrical field strength maximum at the rim of the metallic aperture can be achieved by adjusting the polarization direction [7],... 

As well as color, linear polarization presents a ratio of intensities of the scattered light, P = (I - Ijj / (I + ///, where I and /// are the intensity components perpendicular and parallel to the scattering plane. Thus, polarization characterizes properties of the particles, and its values are not directly influenced by the distances to the Sun and observer, and the spatial... 

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