Scattering Brillouin

Let V be the volume of the scattering particle, r the distance between the scattering particle and an observation point, ySe the adiabatic compressibility, Cp the specific heat at constant pressure, e the dielectric constant, p the density, S the entropy, P the pressure, and k the Boltzmann constant, the scattering intensity, /s given by 

In general, it is very difficult to measure Brillouin spectra because the intensity ratio of Brillouin scattering is about IJ2I-, = 10-6— 10-7 in pure solvent. However, it is an excellent technique to study the structure and dynamics of the liquid or the solid state. 

The application of Brillouin scattering to the characterization of PDMS networks was found to he particularly useful for looking at glassy-state properties of such elastomers at very high frequencies.  

PLCs with a polymethacrylate backbone is dominated by the orientation of the mesogenic groups. 

Polymer B differs from polymers A and C in that it goes through a nematic-smectic-A transition (T = 357K) before reaching room temperature. However, as seen from Table 14.11, the low temperature values of Cjj, C33 and C 3 are quite similar for all three polymers. The axial shear modulus for polymer B is lower by a factor of two. Whether this can be attributed to its smectic state or chemical structure is an open question. 

The pressure wave AP obeys an equation of motion of the form  

The velocity of sound can be expressed in terms of the compnessibiUty Q or the bulk modulus 3  

The presence of the Brillouin doublet in the scattered wave from the medium in which there is an acoustic wave may be seen as follows. For simplicity, we will ignore all tensor characteristics of the problem. Let the pressure wave be of the form 

As a result of this change in pressure, a dielectric constant change occurs and is given by 

---

Gleeson H F 1998 Brillouin scattering from liquid crystals Handbook of Liquid Crystais Voi 1. 

Product analysis polymer network s-NMR, gelation, swelling, birefringence, IR, NMR, STM, SANS, Brillouin scattering, pulse-propagation... 

Zou, L., Ferrier, G.A., Afshar, Sv Yu, Q., Chen, L., and Bao, X. Distributed Brillouin scattering sensor for discrimination of wall-thinning defects in steel pipe under internal pressure, Applied Optics, 43(7), 1583-1588,2004. 

In the Brillouin scattering method the side peaks serve as references and a measurement of the ratio of the intensity of the central peak to the sum of intensities... 

Brillouin scattering Absolute Requires knowledge of certain physical properties of solvent several concentrations necessary 2... 

With the availability of lasers, Brillouin scattering can now be used more confidently to study electron-phonon interactions and to probe the energy, damping and relative weight of the various hydro-dynamic collective modes in anharmonic insulating crystals.The connection between the intensity and spectral distribution of scattered light and the nuclear displacement-displacement correlation function has been extensively discussed by Griffin 236). 

Brillouin scattering of laser light in liquids has been studied by several authors. Shapiro etal. 233) measured hypersonic velocities in various liquids and obtained a Brillouin linewidth of 0.011 cm" in methylene chloride but of less than 0.002 cm in benzene, carbon disulfide and chloroform. The broadening of the Brillouin components arises from damping of thermal phonons and is closely connected with the viscosity coefficient of the medium. From the measured linewidths, the lifetimes of the phonons responsible for Brillouin scattering at 89 45 were calculated to be 4.8 x 10 sec for methylene chloride and 7.6 x 10 sec for toluene. 

Brillouin scattering and its temperature dependence in a liquid crystal was reported by Nordland 238),... 

Besides the spectroscopic investigations of solids by laser-excited spontaneous Raman or Brillouin scattering already discussed in Sections III.6 and 7, much new insight into the optical properties and the structure of solids has been gained by studying nonlinear optical effects. (Surveys and more detailed information about nonlinear optics can be found in refs. 306-308))... 

Figure 14 shows the result of a Brillouin scattering experiment in the vicinity of Tc [11]. Closed circles and open circles below Tc indicate the modes split from the doubly degenerated ferroelectric soft mode. The closed circles above Tc denote the frequency of the doubly degenerated soft u mode in the paraelectric phase. The results clearly show a softening of the soft mode toward zero frequency at Tc following the Curie-Weiss law. The soft mode remains underdamped even at Tc. Generally, a soft mode is heavily damped in the vicinity of Tc, e.g., as for PbTiOs, which are typical displacive-type... 

---