Brillouin spectroscopy has been applied to study a synthetic polymer and its solutions in polar and nonpolar solvents. Of
particular interest has been the effect of concentration, temperature and polarity of the solvent on the mechanical
properties of the mixtures studied. The experimental methods applied permitted investigation of the structural relaxation
process related to the dynamics of changes in the internal structure of the polymer chains. It has been shown that the
quantitative analysis of the relaxation process can be made in terms of the model based on the theory of viscoelasticity of
liquids. The association processes in the systems studied have been analysed assuming the Natta-Baccaredda model. The
model has been shown to be successfully applicable for description of mixtures of the polymers interacting with solvents.
The limitations of the model in the situation when one of the components of the solution is neutral, while the other one
undergoes strong self-association, has been considered.
This paper presents results of a study of aerosol pollution distribution and dynamics measured by lidar observations over the city of Athens. The seasonal dynamics of vertical changes in the backscattering coefficient, extinction coefficient and lidar ratio for lower troposphere has been determined.
Temperature dependence of Brillouin light scattering in selected dimethacrylates has been studied. For the compounds studied, being multifunctional monomers, the values of hypersound speed have been determined. It has been established that with increasing temperature the hypersound speed decreases for all substances studied.
The Rayleight scattering spectra of polyethyleneglycols with different average molecular weight are presented. In the study we used the compounds with average molecular weight 1500 and 2000. The temperature and concentration dependencies of the Rayleigh scattering spectra have given the possibility to determine Rayleigh parameters, also isotropy and anisotropy scattering molecular factors.
The subject of the study was transportation of glucose molecules through a cuprophase membrane by the earlier devised method based on the phenomenon of light interference sensitive to changes in the optical density in two neighbouring chambers separated by a membrane. In the experiment the number of light and dark interference fringes and the rate of their movement through the observation slit were recorded. The analysis of time changes in the concentration of the solutions in the two chambers brings information on the dynamics and mechanism of glucose molecules transportation through the membrane.
Both marine and urban aerosols, which differ in their origin and chemical composition, are subjected to strong dynamic processes in the coastal areas, especially over strongly urbanised areas. The simultanteous presence of both types of aerosols leads to their effective mixing due to the action of winds and convection. This work presents examples of interactions of the two types of aerosols and the impact of the dynamic atmospheric processes on migration of aerosol masses, at two locations in Athens and Kolobrzeg.
The Raman scattering spectra of polyethyleneglycols with different mean molecular weight have been obtained vs. concentration and temperature. The measurements were performed for compounds of mean molecular weight 1500 and 2000. On the basis of the characteristic frequency data of atomic group vibration in organic compounds, the bands observed in Raman spectra have been assigned. The temperature ranges of the phase transition and the change in the order parameters have been estimated from the temperature dependence of the phonon band parameters of the polymers studied. Moreover, the shape of the O - H band vs. polymer concentration has been examined.
The paper gives a general inversion algorithm for lidar's data derivation and profiles of the extinction coefficient, backscattering coefficient and lidar ratio for the lower troposphere. To the best of our knowledge these are the first results obtained with this algorithm.
Results of temperature dependence of the optical Kerr effect in a series of homologous polyoxyethylenediols are presented. The molecular Kerr constant was found to increase with growing molecular weight of a polydiol. The temperature dependence ofthe optical Kerr effect clearly indicates the influence of viscosity in these media.
Optical methods, which are noninvasive and require small volumes of substance studied, are particularly useful for investigation of local structure and molecular interactions. These methods also proved suitable for investigation of monomers and polymers, which are so common in our civilisation and whose degradation poses an important problem in the aspect of the environment protection. Recognition of the processes taking place in polymers, in particular under the effect of optical irradiation, is a necessary prerequisite for design of materials of exactly predicted properties and able to undergo degradation after use. The paper reports results of investigation of a group of liquid aliphatic diols and their derivatives (unsaturated diesters belonging to dimethacrylanes) carried out using two optical methods the optical Kerr effect and Brillouin scattering. These compounds in the form of polymers have been commonly applied in microelectronics and optical waveguides. Temperature dependencies of these two effects have been studied in the range from 280 to 330K, determining in particular temperature changes of Kerr constants, hypersonic velocities and adiabatic compressibility. The values of the parameters measured were found to depend on the number of elements in the ester group and the temperature dependencies of hypersonic velocity, adiabatic compressibility, and optical Kerr constant were markedly non-linear. The results are presented in the form of tables and diagrams. A discussion of molecular interactions in the liquid esters studied and their relation to the changes in the local structure of the medium is also included.
Temperature dependence of the optical Kerr effect was studied in solutions of 1.4, 2.6, and 4.5% n,n- dimethylnitramine in benzene. The optical Kerr constant was observed to decrease with increasing temperature (from 290 to 360K). For solutions of higher concentrations, the temperature dependencies of the OKE signal indicate an increasing role of intermolecular interactions.
Temperature dependencies of the optical Kerr effect have been studied for a series of four analogous diols (of which three contained a heteroatom). The molar Kerr constant was found to increase with temperature below the room temperature and decrease above. The magnitude and character of this change depended on the kind of the heteroatom.
Influence of the thermal effect on nonlinear optical phenomenon of Kerr effect was studied for two laser beams. This effect is important for subnanosecond or picosecond laser working at a high repetition ratio. Its neglect leads to an even 50% underestimation of the values measured.
The paper reports results of the temperature studies of the optical Kerr effect in p-nitrotoluene and p-dichlorobenzene. The measurements were carried out in the temperature range from 330 to 360 K. The values of Kerr constants for both liquids were determined. The temperature dependence of the optical Kerr effect for p-nitrotoluene revealed deviations from the theoretical predictions which indicates the presence of strong dipolar interactions in this liquid, hindering optical orientation of its molecules.
The paper reports results of the optical Kerr effect investigation in the mixture of carbon disulphide and the air. Measurements were performed as a function of temperature and CS2 concentration. Assuming the statistical-molecular theory of the optically induced birefringence, the values of the optical and molar Kerr constants as well as polarizability and optical anisotropy were found. The observed deviations of the temperature dependence of Kerr effect from the theoretical predictions indicate the presence of strong molecular interactions in the studied mixtures.
The paper reports results of investigation of the phenomenon of optical orientation induced by a strong laser beam (optical field) in optically isotropic media. The mechanisms of the phenomenon are indicated and its statistical -- molecular theory is given. Investigation of the phenomenon of optical orientation can provide important information on transparent media allowing a determination of their local structure and microscopic parameters of molecules. This method is particularly useful in the studies of the character and strength of interactions in the gas phase in which these parameters can be easily controlled by changing the gas temperature and pressure. The apparatus used for measuring the effect is briefly described but the main attention has been paid to optical Kerr effect measurements in gases, in particular in carbon dioxide, which is highly suitable for these kinds of measurements as it is easy to study it in different phases and moreover in the vicinity of the critical point. Investigation of carbon dioxide in gas phase was performed in the nanosecond time domain and in a wide range of pressures and temperatures. A detailed interpretation of the results presented in tables and figures is given, and a new method for determination of the orientational relaxation time on optical Kerr effect measurements in the nanosecond time range, is proposed.
We report the results of a temperature study of the optical Kerr effect in 1,4-butanediol dimethacrylate revealing a phase-transition-like change in the temperature range from 295 to 302 K. Using the Brillouin light-scattering method, we studied the temperature behavior of the sound velocity and the elasto-optic constant of 1,4-butanediol dimethacrylate. The preceding temperature dependences display also characteristic discontinuity at about 298 K. To verify these results, a study of the Raman light scattering in 1,4-butanediol dimethacrylate was performed in the same temperature range. It was found that the temperature dependence of the relative intensities of the bands corresponding to the C = C, C = 0, and = C-H bonds reveals a discontinuity at about 294 to 297 K, which coincides with the observed temperature discontinuity of the optical Kerr effect and the Brillouin light scattering. The obtained results are discussed in terms of changes in molecular interactions and the arrangement in the liquid compound investigated.
The investigation of phase transition in butanediol-1,4 dimethacrylate (BDM) using Brillouin light scattering has been performed. Using this method we have studied the temperature behavior of the hypersonic velocity of BDM in the range of 290 - 323 K. The above temperature dependence displays a characteristic discontinuity in the vicinity of 298 K.
One of the nonlinear optics phenomena, discovered after lasers have been put to use, is birefringence of transparent media induced by a laser beam, known as optical Kerr effect. The report presents the development of the technique of optical Kerr effect and a review of the theories of this effect including fundamental formulas and dependencies used for interpretation of experimental data. Recent experimental techniques: nanosecond, picosecond, and femtosecond are discussed and schematic diagrams of most frequently used two- and four- component systems are given and compared. A method, developed by the author, permitting considerable improvement of sensitivity of measuring equipment is described. The application of this method enabled observation of optical Kerr effect in vapors and gases and thus systematic investigation of Kerr effect versus gas pressure and temperature. The exemplary results of optical Kerr effect measurements in liquid and gas media are given as a function of temperature, solution concentration, or gas pressure with particular emphasis put on their cognitive value. Practical applications of Kerr effect are specified. The results of OKE investigation of molecule conformation and local structure of organic liquids, water, and water solution of optically active substances which are a simple model of biological media are presented. Perspectives of further studies of optically induced birefringence of the media using the femtosecond technique are also outlined.
A study of the temperature dependence of optical Kerr effect in butanediol-1,4 dimethacrylate has been performed. The obtained results indicate the presence of a phase transition near 298 K with temperature hysteresis of Kerr effect.
Systematic measurements of optically induced birefringence in some optical active solutions are reported. Relative Kerr constants `Br' (relative to solvent), refractive indices na (at (lambda) equals 488.0 nm) and ni (at (lambda) equals 694.3 nm), and densities `d' of the solutions under study were measured at room temperature in a wide range of concentrations. The absolute and molar Kerr constants `Bo' and `Bm' were calculated as a function of the volume fraction. From these data, the microscopic parameters of the samples such as the specific Kerr constant, mean polarizability, anisotropic factors, optical polarizability, orientation function, orientation parameters, and effective induced dipole moment were calculated.
The first systematic measurements of the temperature dependence of optically induced birefringence in double-distilled water and optically active solutions in the temperature interval from 275 K to 328 K are reported. Also, the absolute value of the optical Kerr constant for water at room temperature (293 K) is measured. We found good agreement between earlier work and ours. The refractive indices and densities of the solutions also were measured in the same temperature interval. From our measurements, the nonlinear molar optical Kerr constant, orientational-redistributional molar optical Kerr constant, mean third-order polarizability and mean nonlinear polarizability for water, and optically active medium also have been determined.
Optical Kerr effect investigations in liquid and gaseous carbon dioxide and the temperature dependence of this effect are reported. From our studies information concerning the molecular interactions and local structure of the medium were obtained. Using the method of indirect comparrison of the results of optical Kerr effect for liquids and gases it is found that the contribution to optical birefringence from a single CO2 molecule in gas and vapor phase is about 7 and 3. 5 times greater respectively than the contribution of the same molecule when in liquid phase. It is also shown that. the effective molecular anisotropy of the carbon dioxide molecule in the liquid phase is markedly lower than its value in the gas phase. This fact is interpreted as an effect of molecular interactions among CO2 molecules which are much stronger in the dense medium.
We report the first systematic measurements of the temperature dependence of optically induced birefringence in benzene 2bromo-- anisole 2-methoxybenzaldehyde and 4methoxybenzaldehyde. The optical Kerr constants relative to benzene are found to be: 1. 00 2. 45 5. 21 4. 89 and 4. 91. respectively. The refractive indices and densities of the liquids for the temperatures studied were also determined. From our measurements the molar Kerr constants and the effective molecular anisotropies were calculated as functions of temperature. The mean value of the secondorder optical hyperpolariZa bility have also been found. We draw some conclusions on the molecular interactions in the liquids. T If" LI I IJIJJJ Nonlinear optical effects in liquids are shaped not only by the optical properties of the isolated atoms (molecules) but moreover by their electric properties and mutual interactions. Hence optical birefringence induced by strong laser light also referred to as the Optical Kerr Effect (OEK) is a source of highly relevant information concerning the structure the electrical properties and the optical properties of atoms and molecules including their interactions in dense media. OKE measurements yield the optical Kerr constant which characterized the macroscopic properties of the medium. If carried out versus temperature OKE measurements additionally provide information on the local structure of the medium and 146 / SPIE Vol. 1391 Laser Technology Ill (1990) 0-8194-0458-6/91 /$4. 0
Optically induced birefringence has been studied in aliphatic aidehydes using the technique of optical Kerr effect. The relative value of the optical Kerr constants were determined. The influence of r electrons localization in a molecule on the studied effect has been found. a
The optical Kerr effect (OKE), a well known non-demolition optical method
for the investigation of matter, yields useful information concerning molecular
interactions and local fields in a medium. However, the interpretation of the results
obtained in dense media is beset with many difficulties, especially when it comes to
determine the contributions of different types of molecular interactions to the optically
induced birefringence. Due to the enhancement in sensitivity of our experimental
device,1 OKE measurements in gases and vapours, where the molecular interactions
can be pressure-controlled, have now become feasible.
Here, we report OKE measurements in liquid and gaseous carbon dioxide and
the temperature-dependence of this effect, from which some information concerning
the molecular interactions and local molecular fields of the medium can be obtained.
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