Light polarization vector

Figure 6.16. Angular dependent NEXAFS spectra of TTF-TCNQ for (a) S2p, (b) Cli and (c) Nl. The e angle is defined as the angle between the light polarization vector and the surface plane. Reprinted with permission from J. Fraxedas, Y. J. Lee, 1. Jimenez, R. Gago, R. M. Nieminen, R Ordejdn and E. Canadell, Physical Review B, 68, 195115 (2003). Copyright (2003) by the American Physical Society.

Fig. 7.34 The narrow energy range UPS spectra of 4-BCMU PDA, for the light polarization vector, E, parallel or perpendicular to the direction of the n-system.

Fig. 11.2 Normal light incidence on a planar layer of a nematic liquid crystal with homeotropic (a) and tilted (b) alignment (k is light propagation vector, e is light polarization vector, n is the director)...

For both transitions the dipole moment Ptr is directed exactly along the longitudinal molecular axis. Thus, if such molecules form the nematic phase, the absorption coefficient would depend on the average angle between the light polarization vector e and the longitudinal molecular axes, i.e., between e and the director n. 

In a quantum mechanical treatment the intensity of the fluorescence emitted on a transition 2 - 3 with polarization vector E2 following excitation on a transition 1 ->2 by optical pumping with linearly polarized light (polarization vector E ) is described by the product of the two corresponding matrix elements... 

Figure 2.2 Side-chain polymers, used by Shibaev et al. [11], which show the effect of cis-trans isomerization in a field of polarized UV light. The trans isomer, which is parallel to the UV light polarization vector, is transferred to the cis isomer and then again to the trans isomer, which is perpendicular to the initial one. As a result of this transformation, all the absorption oscillators of azobenzene side-chain molecules align perpendicular to the UV hght polarization. Reprinted from [10], Institute of Physics Publishing (2003)...

The second term on the right-hand side, a component oscillating at frequency 2co, represents the second harmonic of the incident beam. This component of the polarization vector can radiate light at the frequency 2co. Observation of the second harmonic generation was demonstrated in the early 1960s using mby lasers (59). 

The classical scheme for dichroism measurements implies measuring absorbances (optical densities) for light electric vector parallel and perpendicular to the orientation of director of a planarly oriented nematic or smectic sample. This approach requires high quality polarizers and planarly oriented samples. The alternative technique [50, 53] utilizes a comparison of the absorbance in the isotropic phase (Dj) with that of a homeotropically oriented smectic phase (Dh). In this case, the apparent order parameter for each vibrational oscillator of interest S (related to a certain molecular fragment) may be calculated as S = l-(Dh/Di) (l/f), where / is the thermal correction factor. The angles of orientation of vibrational oscillators (0) with respect to the normal to the smectic layers may be determined according to the equation... 

The other technique utilizes the different surface sensitivity for s-and p-polarized light - the former has its polarization vector perpendicular, the latter parallel to the plane of incidence. Due to the different... 

Under the following conditions (i) the polarization vector of the probe light is perpendicular to the applied electric field, (ii) the molecular orientation in solid... 

Light-matter interactions can be described via an induced polarization, i.e., the induced dipole moment per unit volume. Ultrafast laser pulses, which are used in laser scanning microscopes, have high enough intensity to induce a nonlinear polarization in various materials. For intense optical electric field E, the polarization vector P can be expanded in the power series (Boyd 1992)... 

Nonlinear optics deals with physical systems described by Maxwell equations with an nonlinear polarization vector. One of the best known nonlinear optical processes is the second-harmonic generation (SHG) of light. In this section we consider a well-known set of equations describing generation of the second harmonic of light in a medium with second-order nonlinear susceptibility %(2 The classical approach of this section is extended to a quantum case in Section IV. 

Brewster window A flat optical window tilted at an angle such that light whose electric vector is polarized parallel to the plane of the window is 100% transmitted. Light polarized perpendicular to the window is partially reflected. It is used on the ends of a laser to produce light whose electric field oscillates perpendicularly to the long axis of the laser. 

Anisotropy. Light emitted from excited molecules immediately after absorption is always partially polarized, whether or not the exciting beam consists of plane polarized light. When light polarized in a vertical plane is used for excitation, part of the emitted light (of intensity lv) will have its electric vector parallel to that of the exciting light. The remainder of intensity /, will be polarized in a horizontal plane. The polarization P of the emitted radiation is defined by Eq. 23-19 and the anisotropy R by Eq. 23-20. After excitation by a laser pulse both the fluorescence and its anisotropy decay with time and can be measured. The decay of R (but not of P) can usually be described as the sum... 

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