Spectroscopy polarized absorption

Bigio, L. and Grant, E.R. (1987b). Polarized absorption spectroscopy of A-doublet molecules Transition moment vs electron density distribution, J. Chem. Phys. 87, 5589-5597. 

Polarized absorption spectroscopy is a powerful diagnostic tool for investigating molecular structure and the symmetry considerations discussed above can be extended to the situation where the incident light is polarized along a particular direction. The strength of the interaction of the transition dipole moment, A(. -,k , with the electric vector of the... 

The pump pulse in time-resolved pump-probe absorption spectroscopy is often linearly polarized, so photoexcitation generally creates an anisotropic distribution of excited molecules. In essence, the polarized light photoselects those molecules whose transition moments are nominally aligned with respect to the pump polarization vector (12,13). If the anisotropy generated by the pump pulse is probed on a time scale that is fast compared to the rotational motion of the probed transition, the measured anisotropy can be used to determine the angle between the pumped and probed transitions. Therefore, time-resolved polarized absorption spectroscopy can be used to acquire information related to molecular structure and structural dynamics. 

Uznanski, P., Kryzsewski, M., and Thulstrup, E. W. Polarized Absorption Spectroscopy of Azobenzene and frans-Stilbene in Stretched Polyethylene Films. Spectrochini- Acta Part A 46, 23 (1990). 

Samples oriented by photoselection have been used for studies of molecular anisotropy by polarized absorption spectroscopy. For instance, the... 

The most surprising result from the crystallographic analysis of the bacterial RC was the discovery of the locad two-fold symmetry of the cofactor arrangement. Successful structural analysis has also allowed more detailed analysis of RC functions. An important initial result was obtained by applying polarized absorption spectroscopy to crystals from Rp. viridis RC. Zinth et al. (1985) and Kirmaier et al. 

Polarized absorption spectroscopy was used to assess the orientation of PEPy-C18 polymer molecules on ordered saponite layers. Figure 8.8 shows the polarized absorption spectra of PEPy-C18/saponite 32-bilayer films. The relatively large difference in optical... 

In relation to the molecular alignment, incident angle-dependent polarized absorption spectroscopy [31, 32] of thin films gives important information on the electronic states of the molecules and their interaction in the solid disordered system (i.e. thin films). This method is based on measuring the polarized... 

The commonly used LCR meters offer quick and easily computerized measurements in many frequencies, usually up to about 10 MHz. At higher frequencies, up to about 2 GHz, microwave teclmologies are needed. At even higher frequencies, which would test the displacement polarization, absorption spectroscopy (IR intramolecular reorientation UV-VIS electronic polarization) techniques are used. 

The stability of the induced I phase at the irradiated site of polymer azobenzene LC strongly depends on temperature. At temperatures above the induced I phase disappeared and the N phase was restored after some time, which depended on temperature. At high temperatures such as 140°C, the I phase disappeared in seconds. At temperatures just above Tg the induced I phase remained fairly stable for some time, but disappeared after a prolonged time. On the other hand, at temperature below Tg the induced I phase remained unchanged even after 1 year and 6 months. The cis-trans back-isomerization took place thermally even at room temperature, and the trans-ioun was restored almost completely in 1 day. Polarized absorption spectroscopy showed that even though the trans-iorm was restored in 1 day at room temperature, orientation of the /ra 5-azobenzene mesogens was different from that of the initial state. Before photoirradiation, the azobenzenes were aligned in one direction to form uniaxial monodomain, but after photoirradiation the cw-form was produced, and N—I phase transition was induced. However, after the trans-ioim was restored thermally, the orientation... 

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