Linear dichroism spectrum

Figure 4-6. Absorption and linear dichroism spectra for the PSRC of Rps. viridis. (a) SAC-CI theoretical excitation spectrum [67], (b) Experimental absorption and linear dichroism spectra [146], (c) SAC-CI theoretical linear dichroism spectrum [67]...

Linear dichroism spectrum of intact phycobiiisomes in squeezed gels measured... 

Figure 2. The i.c.d. spectrum (a) of the 3-c.d. inclusion complex. The linear dichroism spectrum (B) (full line, polarized along the long axis dotted line, polarized along the short axis) at -ihO °C. The electronic spectrum (C) at room temperature in cyclohexane.

The 1 and s denote the long and short axes, respectively. Obtained from the linear dichroism spectrum. 

The linear dichroism spectrum is a diagram reporting the difference between the absorption of the radiation with parallel polarizahon (An) and that of the radiation with perpendicular polarization (Ax) with respect to the direction of preferenhal orientation of the molecules, as a function of wavelength. 

Fig. 1 Top Behavior of the electronic linear chiroptical response in the vicinity of an excitation frequency. Re = real part (e.g., molar rotation [< ]), Im = imaginary part (e.g., molar ellipticity [0]). Without absorption line broadening, the imaginary part is a line-spectrum (5-functions) with corresponding singularities in the real part at coex. A broadened imaginary part is accompanied by a nonsingular anomalous OR dispersion (real part). A Gaussian broadening was used for this figure [37]. Bottom Several excitations. Electronic absorptions shown as a circular dichroism spectrum with well separated bands. The molar rotation exhibits regions of anomalous dispersion in the vicinity of the excitations [34, 36, 37]. See text for further details...

A number of physical studies have been performed on Mn111 porphyrins in an attempt to understand their electronic structure. The visible spectra of such compounds have been of particular interest. For most metal porphyrins the visible spectrum is insensitive to the nature of the coordinated metal and this has been interpreted as indicating little interaction between the metal and the porphyrin 7r-orbitals in such compounds. However this is not the case for Mn111 porphyrins which exhibit metal-dependent charge transfer absorptions. This dependence appears to reflect significant n orbital-Mn"1 interaction. Resonance Raman and linear dichroism spectral studies are also consistent with this conclusion.667... 

Such a spectrum is interpreted in terms of exciton interactions between the retinals within the trimer clusters (41,42,279-282) which characterize the purple membrane lattice (cf. Section I-B). Although this conclusion is generally accepted, the details of the exciton-interaction model may have to be revised. For example, the current exciton models (41,42) predict a low-intensity, out-of-the-membrane-plane optical transition on the high-energy side of the main absorption band, which is in varianceo with linear dichroism spectra (254). Moreover, the 9- to 12-A distance between chromophores predicted by these models are not compatible with recent neutron diffraction data (283). 

Figure 4.6-5 Infrared linear dichroism of a nematic sample (EBBA/MBBA equimolar mixture of N-(p-ethoxybenzylidene)-//- -butylaniline and its methoxy analogue 2 of Table 4.6-1 Riedel-de Haen) expressed as the difference of the absorption indices k and ke (imaginary part of the complex refractive index) for the ordinary and the extraordinary beam, resp. the temperature increases and thus, the degree of order decreases from spectrum a to spectrum d, the latter was taken close to the clearing point F, where the order and consequently the anisotropy vanishes (Reins et al., 1993).

The development of photochemical active films of chromatophores has also involved the dialysis method. The photoactive sheet derived from Rhodopseudomonas viridis had characteristic properties of a three-dimensional thin crystal, showing linear dichroism in the absorption spectrum. That indicates a correct orientation in the arrangement of the chromatophores. 

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