Anisotropic spectrum

Since good resolution of the Q-branch is hardly achievable by means of the usual Raman spectroscopy the first verification of this formula was carried out on side branches of anisotropic spectra which are easier to resolve (see Fig. 0.2 and Fig. 3.1). Generally speaking the right formula for component widths of these branches must be separately derived [212] but approximate estimation for the S-branch may be done as proposed in [213] ... 

The shapes of both /w and 7hv lines are assumed to be represented by simple Lorentzians. For a totally symmetric vibration with a low polarization ratio as in the present case, the vibrational and reorientational relaxation times Tv and can be determined from the half-widths of the isotropic and anisotropic spectra. Since the value of /hv is much smaller than that of /w for the 1050 cm" line, the contribution of /gv to the isotropic intensity can be neglected ... 

The Rhodonines, like other aromatic members of the carboxylic family are not very soluble in water. They would be expected to be soluble in less polar solvents like ether or alcohol. In dilute solution, their absorption cross section for both their isotropic and anisotropic spectra would be expected to be very small. To the extent they can be excited, their structure would continue to suggest, they will not relax via fluorescence or phosphorescence. 

In order to compare primary dynamics with secondary relaxation steps, we depict on the left-hand side of Fig. 15 the anisotropic spectra (a-c), which consist mainly of spectral components with the same linear polarization as directly induced by the pump pulse. On the right-hand side of the figure the corresponding isotropic spectra (d-f) are shown. In the latter spectral components can notably contribute that result from a relaxation process, where the initially orientation of the OH transition dipole is (partially) lost. 

MV+ or DQ+ radicals incorporated in the cavities of zeolites-Y exhibit EPR spectra analogous to those of the radicals in solution, consisting of a broad single line (A//pp j 17 G) with g-factor values of 2.0030 (MV+ ) and 2.0029 (DQ+ ).24 Although incorporated in the zeolite cavity, the radicals react with dioxygen at -78 °C to form the superoxide radical anion through an electron-transfer reaction, and the spectra are replaced by the anisotropic spectra of the 02 radical anion interacting with either MV2+ (g/ = 2.084 and g2,3 = 2.005)-or DQ2+... 

Under conditions where isotropic tumbling of the molecules is restricted or annealed, as in frozen solutions, powders and other solid-state situations, anisotropic spectra are observed, i.e. additional splitting complicates the spectra, but also provides highly valuable information on the electronic nature and orientation of the ligand set. In the case of vanadyl complexes, the dominant V=0 unit defines the primary axis (the z direction). In this case of so-called axial symmetry, two sets of eight lines are observed with differing g and... 

Broad spectra with little fine structure were obtained in the early studies [132—134] and radical identification was not possible. Assignment of the radicals has, however, been possible by the use of oriented Mylar films [135, 136]. Analysis of the anisotropic spectra obtained has shown that two radicals are formed. The most abundant results from H atom abstraction from the chain end and the second is a substituted phenyl radical. Since very similar values were obtained for the initial yields of radicals and of hydrogen formation, the mechanism proposed for the radiolysis of polyethyleneterephthalate was... 

Complex, anisotropic spectra were observed in 6H and 4H polytypes doped with Sc [5,8,9]. The g-factors parallel to the crystal axis are smaller than those that are perpendicular to it (see TABLE 2). This anisotropy is opposite to that of the shallow acceptors. Many spectra are observed whose parameters indicate that the Sc-acceptors, like the B-centres, are not effective-mass-like. 

Samples also were examined for the presence of an anisotropic spectra to detect any splitting of the into Degrees of reduction of sym-... 

Freed et al. [3] evaluated the relaxation rate of polymer chains by the analysis of the anisotropic spectra of nitroxide spin labels. The main triplet spectrum was due to hyperfine coupling caused by the nitrogen nucleus. It narrowed with an increase in mobility of the radicals because of motional averaging of the anisotropic hyperfine interaction. The rotational correlation time of nitroxide spin labels can be estimated using the procedure of Freed et al. by taking into account the anisotropic rotational motion. The ESR line width, AHmsi of the spectrum can be expressed as follows ... 

This represents the spectral width between points of maximum and minimum amplitude (i.e., the distance in Gauss between g. and g for the anisotropic spectra). 

Rates of motion are reflected in the width of the ESR lines slower motion (i.e. increased correlation times) broadens the individual lines (Seelig, 1976). Although correlation times may be obtained by line width analysis for isotropic spectra, similar interpretations of anisotropic spectra are very tedious, and require computer modelling. Owing to these complications, the rate of spin label motion is rarely taken into account in the analysis of ESR spectra. 

Anisotropic Spectra. Programs are available for the simulation of single crystal, partially oriented, and powder simulation (sometimes in the same program) and in several cases allowance for noncoincidence of the axes of the g and A tensors can be included. Various programs are described in detail in [53]. [56], [57]. 

All. Rotation-Vibration Correlation in Infrared and Anisotropic Spectra of. diluted Van der Waals Solutions. Effect of Intermolecular Forces. 

Particularly informative can be H-NMR spectra of deuterated guest molecules included in uniaxially oriented 8 form SPS films. In fact, highly anisotropic spectra of most volatile organic compounds can already be achieved at room temperature, which allow separation of components of solid-state H-NMR molecular spectra. 

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