Magnetic optical rotation dispersion

From another point of view MCD can be regarded as the absorptive counterpart of magnetic optical rotation dispersion (MORD) the well-known Faraday effect. This is the reason why in the past the spectra were given in the units of natural optical rotation per magnetic field... 

Faraday found experimentally that all substances show this effect in presence of a magnetic field (Schatz and Me Caffery, 1969), leading to Magnetic optical rotation dispersion (MORD) and Magnetic circular dichroism (MCD) (Caldwell and Eyring, 1976 Dawber, 1964 Foss and Mccarvil, 1965 Schatz et al., 1978 Thome, 1977). Experimentally however, ORD and MORD were never measured extensively contrary to CD and MCD. 

Figure 3 The Faraday Effect within magnetic optical rotatory dispersion (MORD) spectroscopy. A plane polarized beam is rotated by a magnetic field applied parallel to the axis of propagation. The rotation is defined as positive if the beam is rotated to the right in a clockwise direction when viewed toward the source (a). The original definition of Icp and rep within CD spectroscopy—fight plane polarized in the yz-plane can be described in mathematical terms as being comprised of left or right circularly polarized components of equal phase and amplitude (b). The perspective is depicted schematically toward the source. (Reprinted from Mack, Stillman and Kobayashi, Elsevier 2007)...

The pitch P is the most important parameter of cholesteric liquid crystals. The physical properties of cholesteric liquid crystals are associated with P, such as selective reflection, optical rotation dispersion, circular dichroism, etc. The helical pitch is sensitive to the temperature and external field, for example, electric and magnetic field, chemical environment, pressure or radiation, etc. 

Optical rotatory dispersion and circular dichroism (83, 84) can often be of great value, and the spectra are particularly sensitive to the conformation of the protein. Much work remains to be done in this field before the results can be definitely interpreted in terms of the electronic structure of the metal. Magneto-optical rotation and magnetic circular dichroism (MOR and MCD), which are beginning to be applied to porphyrins and haemoproteins, offer much greater promise (30, 85). 

The relationship between parachor and structure of arsines has been described (503), Magnetic studies have been made on some phenyl arsenicals (504). An optical rotatory dispersion study of a spiroarsonium compound revealed that the rotation was about twice that of the corresponding phosphorus derivative (505). 

In this model, the symbols have the following meaning. ( )R(a3) ao(l)HD(a3) is the optical rotation produced by the vapour and depends on the number of absorption lengths ao and on the lineshape function D(o)) which takes the form of a Doppler-broadened dispersion curve for magnetic and electric field induced rotation ( )r will depend on the strength of the field and D(oa) on the direction and type of field (see table 2). The transmitted intensity 1 - Ij exp[-aoG(o))] where the lineshape function G(o)) for a single spectral component can usually be accurately described by a Doppler-broadened Lorentzian curve. Finally the terms B and C in equation (53) represent respectively the finite extinction ratio of the polarisers and a laser independent... 

The two circular-polarized beams of the incident radiation (I, levorotatory r, dextrorotatory) not only can be influenced with respect to their direction of rotation, but also, in the region of an absorption band, can be absorbed to a different extent by the sample, so that in addition to so-called optical rotatory dispersion (ORD), circular dichroism (CD) or the Cotton effect is observed [35] - (38J. Along with these classical methods of analysis, modem methods for the analytical investigation of surfaces and boundary layers have become very important, including the use of polarized light in ellipsometry ( Surface Analysis) and surface plasmon resonance. Under the influence of external forces (e.g., a magnetic field), even optically inactive substances can be caused to produce magnetooptic rotation. 

The first contribution to the induced electric dipole moment in O Eq. 11.74 from the time dependence of the magnetic field, w G, gives rise to two different observable properties. In the dispersive region, this property determines the optical rotatory power, or just optical rotation (OR) for short, and in the absorptive region it determines the rotational strength observed in electronic circular dichroism (ECD). 

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