Elastic molecular light scattering

Table I Information Available from Elastic and Inelastic Molecular Light Scattering...

However, melt elasticity is more closely related to the third moment known as the z-average molecular weight M. The values of are most often determined using either light-scattering photometry or ultracentrifugation. It is shown mathematically as ... 

The size of molecular assembly of six synthetic dialkyl amphiphiles as determined by a quasi-elastic light scattering is varied in the presence of nonionic MEGA-n surfactants (N-D-gluco-N-methylalkanamide C = 7-9). 

Quasi-elastic light scattering was employed successfully to estimate sizes of molecular assemblies in terms of hydrodynamic radius, R . In the present paper, we concentrated on a "phase diagrammatic" study of molecular assembly size. 

Fig. 18.1 A dressed-state model that is used in the text to describe absorption, emission, and elastic (Rayleigh) and inelastic (Raman) light scattering. g) and. v> represent particular vibronic levels associated with the lower (1) and upper (2) electronic states, respectively. These are levels associated with the nuclear potential surfaces of electronic states 1 and 2 (schematically represented hy the parabolas). Rj are radiative continua— 1 -photon-dressed vibronic levels of the lower electronic states. The quasi-continuum L represents a nonradiative channel—the high-energy regime of the vibronic manifold of electronic state 1. Note that the molecular dipole operator /t couples ground (g) and excited (s) molecular states, but the ensuing process occurs between quasi-degenerate dressed states g,k and 5,0).

Schematic models for the expanded structure of bile acid-phosphatidylcholine mixed micelles are shown in Fig. 2B. The original model was proposed by Small in 1967 (S36). In this model the mixed micelle consisted of a phospholipid bilayer disk surrounded on its perimeter by bile acid molecules, which were oriented with their hydrophilic surhices in contact with aqueous solvent and their hydrophobic sur ces interacting with the hydrocarbon chains of the phosphohpid molecules. This model has recently been revised, based on further studies of mixed micelles using quasi-elastic light scattering spectroscopy (M20). In a new model for the molecular structure of bile acid-phospholipid mixed micelles. Mazer et al. (M20) propose a mixed disk, in which bile acids are found not only on the perimeter of phospholipid bilayers, but also incorporated within their interior in high concentrations (Fig. 2B). The size of these mixed micelles was estimated to be as high as 200 to 400 A in radius in some solutions, and disk-shaped particles in this size range were observed by transmission electron microscopy (M20). Micellar aggregates similar in size and structure to those found in model bile solutions have been demonstrated in dog bile (M22).

It is instructive to take as a first example the general expression for molecular polarizability, the response tensor that formally mediates elastic light scattering in the electric dipole approximation. The result is obtained by application of Eq. (74) with m = 2 (one photon is annihilated and another of the same frequency is created). Here there are only two time orderings, or state-sequence pathways, as illustrated in Figs. 5 and 6, respectively. Each generates a term whose numerator is a product of transition dipole moment components. For... 

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