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Techniques of Chiroptical Spectroscopy
Published in Grinberg Nelu, Rodriguez Sonia, Ewing’s Analytical Instrumentation Handbook, Fourth Edition, 2019
Nelu Grinberg, Harry G. Brittain, Sonia Rodriguez
Molecules for which the mirror images cannot be superimposed are denoted as being dissymmetric or chiral, and these enantiomer structures are capable of being resolved. The fundamental requirement for the existence of molecular dissymmetry is that the molecule cannot possess any improper axes of rotation, the minimal interpretation of which implies additional interaction with light whose electric vectors are circularly polarized. This property manifests itself in an apparent rotation of the plane of linearly polarized light (polarimetry) or in a preferential absorption of either left- or right-circularly polarized light (circular dichroism). Circular dichroism (CD) can be observed in either electronic or vibrational bands. The Raman scattering of a chiral compound can also reflect the optical activity of the molecule. Should the excited state of a compound be both luminescent and chiral, then the property of circularly polarized luminescence can be observed. The circular dichroism of an optically active molecule can be used in conjunction with fluorescence monitoring to provide a differential excitation spectrum (fluorescence-detected circular dichroism).
Polarization Measurement
Published in John G. Webster, Halit Eren, Measurement, Instrumentation, and Sensors Handbook, 2017
Polarimetry is a method for measuring the polarization of light and the polarization response of materials. An optical system used for such purposes is called a polarimeter or an ellipsometer. To measure the polarization response of a sample, polarized light is generated and incident on the sample. By examining the polarization states of both incident and reflected or transmitted light, the characteristics of a sample can be determined. A schematic diagram of a polarimeter used to measure the polarization response of a sample is shown in Figure 49.4. The light source and polarizer are used to generate polarized light, and the analyzer and detector are used to analyze the polarization of light [4,20]. An analyzer is a polarizer used to analyze polarized light.
Polarimetry
Published in Toru Yoshizawa, Handbook of Optical Metrology, 2015
A dictionary definition of polarimetry is “the art or process of measuring the polarization of light” [1]. A more scientific definition is that polarimetry is the science of measuring the polarization state of a light beam and the diattenuating, retarding, and depolarizing properties of materials [2]. Similarly, a polarimeter is an optical instrument for determining the polarization state of a light beam, or the polarization-altering properties of a sample [2].
Characterization of three GEM chambers for the SBS front tracker at JLab Hall A
Published in Radiation Effects and Defects in Solids, 2018
L. Re, V. Bellini, V. Brio, E. Cisbani, S. Colilli, F. Giuliani, A. Grimaldi, F. Librizzi, M. Lucentini, F. Mammoliti, P. Musico, F. Noto, R. Perrino, C. Petta, M. Russo, M. Salemi, F. Santavenere, G. Sava, D. Sciliberto, A. Spurio, M.C. Sutera, F. Tortorici
The second and third trackers ( Back Trackers, BTs (6)) will consist of 10 layers, with active area of , of GEM chambers. Each layer consists of a vertical stack of four GEM modules of each one (40 GEM modules as a total). We combined the BTs with two analyzer blocks for proton polarimetry. Proton polarimetry technique allows the determination of the proton FF ratio by the method of polarization transfer from the measurement of the ratio of the longitudinal and transverse components of the proton spin polarization. We will measure the transverse polarization of the recoil proton from the azimuthal asymmetry after re-scattering in one of the two analyzer blocks, by measuring the polar and azimuthal angles of the re-scattered proton in the tracker downstream of the analyzer block, with respect to the angles measured by the upstream tracker.
Uncertainty Analysis in 3D Equilibrium Reconstruction
Published in Fusion Science and Technology, 2018
Mark R. Cianciosa, James D. Hanson, David A. Maurer
Using the equilibrium and profile functions of temperature, density, and soft X-ray emissivity, V3FIT models the signal measured by magnetic diagnostics, soft X-ray emissivity, interferometry, polarimetry, Thomson scattering, motional stark effect, or electron cyclotron emission. Models for limiter geometry are used to constrain the equilibrium by mimicking physical boundaries. Priors can be placed on any reconstruction parameter or parameter derived from the equilibrium model. The model-derived parameters include any quantity derivable from the equilibrium solution but not a direct parameterization. For instance, when the equilibrium is parameterized by the current profile, a rotational transform is derived from the result. By placing priors on the rotational transform, the unknown current profile can be reconstructed to produce a known rotational transform profile.
Interpreting and quantifying depolarization properties of tissue with differential polarization parameters
Published in Waves in Random and Complex Media, 2022
Quantification of the polarization and depolarization properties can provide the effective information for diagnosis, remote sensing and material analysis. At present, the most frequently used method of deriving the polarization parameters from the measured Mueller matrices is the polar decomposition proposed by Lu and Chipman [10,11]. Alali reviewed the applications of obtaining images of polarization parameters of various tissues by using the Lu-Chipman decomposition on both the transmission and the refection polarimetry [12]. However, expressions of the parameters extracted from the polar decomposition are order-dependent. To solve this problem, several other Mueller decomposition methods have been reported [13–22]. One is the normal decomposition proposed by Xing [13]. This method requires a complex calculation procedure of diagonalization of the auxiliary matrices, in which a Mueller matrix is expressed as a product of two non-depolarizing Mueller matrices and a depolarizer matrix containing all the depolarizing properties. By using the home-made polarimeter, Ossikovski compared the images of polarization parameters of tissues that are obtained by the Lu-Chipman decomposition method and the normal method to show that different decompositions of the measured Mueller matrix can be the valuable complementary methods for characterizing polarization properties of media or system [10]. The normal decomposition was developed by Ossikovski and he proposed the symmetric decomposition, in which each non-depolarizing component of normal form is further expressed as a product of the component matrices of retarder and diattenuator [14].